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linux/fs/namei.c
Linus Torvalds 561ec64ae6 VFS: don't do protected {sym,hard}links by default 
In commit 800179c9b8 ("This adds symlink and hardlink restrictions to
the Linux VFS"), the new link protections were enabled by default, in
the hope that no actual application would care, despite it being
technically against legacy UNIX (and documented POSIX) behavior.

However, it does turn out to break some applications.  It's rare, and
it's unfortunate, but it's unacceptable to break existing systems, so
we'll have to default to legacy behavior.

In particular, it has broken the way AFD distributes files, see

  http://www.dwd.de/AFD/

along with some legacy scripts.

Distributions can end up setting this at initrd time or in system
scripts: if you have security problems due to link attacks during your
early boot sequence, you have bigger problems than some kernel sysctl
setting. Do:

	echo 1 > /proc/sys/fs/protected_symlinks
	echo 1 > /proc/sys/fs/protected_hardlinks

to re-enable the link protections.

Alternatively, we may at some point introduce a kernel config option
that sets these kinds of "more secure but not traditional" behavioural
options automatically.

Reported-by: Nick Bowler <nbowler@elliptictech.com>
Reported-by: Holger Kiehl <Holger.Kiehl@dwd.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # v3.6
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-10-26 10:05:07 -07:00

4066 lines
99 KiB
C
Raw Blame History

/*
* linux/fs/namei.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* Some corrections by tytso.
*/
/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
* lookup logic.
*/
/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
*/
#include <linux/init.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/fsnotify.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/ima.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fcntl.h>
#include <linux/device_cgroup.h>
#include <linux/fs_struct.h>
#include <linux/posix_acl.h>
#include <asm/uaccess.h>
#include "internal.h"
#include "mount.h"
/* [Feb-1997 T. Schoebel-Theuer]
* Fundamental changes in the pathname lookup mechanisms (namei)
* were necessary because of omirr. The reason is that omirr needs
* to know the _real_ pathname, not the user-supplied one, in case
* of symlinks (and also when transname replacements occur).
*
* The new code replaces the old recursive symlink resolution with
* an iterative one (in case of non-nested symlink chains). It does
* this with calls to <fs>_follow_link().
* As a side effect, dir_namei(), _namei() and follow_link() are now
* replaced with a single function lookup_dentry() that can handle all
* the special cases of the former code.
*
* With the new dcache, the pathname is stored at each inode, at least as
* long as the refcount of the inode is positive. As a side effect, the
* size of the dcache depends on the inode cache and thus is dynamic.
*
* [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
* resolution to correspond with current state of the code.
*
* Note that the symlink resolution is not *completely* iterative.
* There is still a significant amount of tail- and mid- recursion in
* the algorithm. Also, note that <fs>_readlink() is not used in
* lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
* may return different results than <fs>_follow_link(). Many virtual
* filesystems (including /proc) exhibit this behavior.
*/
/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
* New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
* and the name already exists in form of a symlink, try to create the new
* name indicated by the symlink. The old code always complained that the
* name already exists, due to not following the symlink even if its target
* is nonexistent. The new semantics affects also mknod() and link() when
* the name is a symlink pointing to a non-existent name.
*
* I don't know which semantics is the right one, since I have no access
* to standards. But I found by trial that HP-UX 9.0 has the full "new"
* semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
* "old" one. Personally, I think the new semantics is much more logical.
* Note that "ln old new" where "new" is a symlink pointing to a non-existing
* file does succeed in both HP-UX and SunOs, but not in Solaris
* and in the old Linux semantics.
*/
/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
* semantics. See the comments in "open_namei" and "do_link" below.
*
* [10-Sep-98 Alan Modra] Another symlink change.
*/
/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
* inside the path - always follow.
* in the last component in creation/removal/renaming - never follow.
* if LOOKUP_FOLLOW passed - follow.
* if the pathname has trailing slashes - follow.
* otherwise - don't follow.
* (applied in that order).
*
* [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
* restored for 2.4. This is the last surviving part of old 4.2BSD bug.
* During the 2.4 we need to fix the userland stuff depending on it -
* hopefully we will be able to get rid of that wart in 2.5. So far only
* XEmacs seems to be relying on it...
*/
/*
* [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
* implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
* any extra contention...
*/
/* In order to reduce some races, while at the same time doing additional
* checking and hopefully speeding things up, we copy filenames to the
* kernel data space before using them..
*
* POSIX.1 2.4: an empty pathname is invalid (ENOENT).
* PATH_MAX includes the nul terminator --RR.
*/
void final_putname(struct filename *name)
{
if (name->separate) {
__putname(name->name);
kfree(name);
} else {
__putname(name);
}
}
#define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
static struct filename *
getname_flags(const char __user *filename, int flags, int *empty)
{
struct filename *result, *err;
int len;
long max;
char *kname;
result = audit_reusename(filename);
if (result)
return result;
result = __getname();
if (unlikely(!result))
return ERR_PTR(-ENOMEM);
/*
* First, try to embed the struct filename inside the names_cache
* allocation
*/
kname = (char *)result + sizeof(*result);
result->name = kname;
result->separate = false;
max = EMBEDDED_NAME_MAX;
recopy:
len = strncpy_from_user(kname, filename, max);
if (unlikely(len < 0)) {
err = ERR_PTR(len);
goto error;
}
/*
* Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
* separate struct filename so we can dedicate the entire
* names_cache allocation for the pathname, and re-do the copy from
* userland.
*/
if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
kname = (char *)result;
result = kzalloc(sizeof(*result), GFP_KERNEL);
if (!result) {
err = ERR_PTR(-ENOMEM);
result = (struct filename *)kname;
goto error;
}
result->name = kname;
result->separate = true;
max = PATH_MAX;
goto recopy;
}
/* The empty path is special. */
if (unlikely(!len)) {
if (empty)
*empty = 1;
err = ERR_PTR(-ENOENT);
if (!(flags & LOOKUP_EMPTY))
goto error;
}
err = ERR_PTR(-ENAMETOOLONG);
if (unlikely(len >= PATH_MAX))
goto error;
result->uptr = filename;
audit_getname(result);
return result;
error:
final_putname(result);
return err;
}
struct filename *
getname(const char __user * filename)
{
return getname_flags(filename, 0, NULL);
}
EXPORT_SYMBOL(getname);
#ifdef CONFIG_AUDITSYSCALL
void putname(struct filename *name)
{
if (unlikely(!audit_dummy_context()))
return audit_putname(name);
final_putname(name);
}
#endif
static int check_acl(struct inode *inode, int mask)
{
#ifdef CONFIG_FS_POSIX_ACL
struct posix_acl *acl;
if (mask & MAY_NOT_BLOCK) {
acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
if (!acl)
return -EAGAIN;
/* no ->get_acl() calls in RCU mode... */
if (acl == ACL_NOT_CACHED)
return -ECHILD;
return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
}
acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
/*
* A filesystem can force a ACL callback by just never filling the
* ACL cache. But normally you'd fill the cache either at inode
* instantiation time, or on the first ->get_acl call.
*
* If the filesystem doesn't have a get_acl() function at all, we'll
* just create the negative cache entry.
*/
if (acl == ACL_NOT_CACHED) {
if (inode->i_op->get_acl) {
acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
if (IS_ERR(acl))
return PTR_ERR(acl);
} else {
set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
return -EAGAIN;
}
}
if (acl) {
int error = posix_acl_permission(inode, acl, mask);
posix_acl_release(acl);
return error;
}
#endif
return -EAGAIN;
}
/*
* This does the basic permission checking
*/
static int acl_permission_check(struct inode *inode, int mask)
{
unsigned int mode = inode->i_mode;
if (likely(uid_eq(current_fsuid(), inode->i_uid)))
mode >>= 6;
else {
if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
int error = check_acl(inode, mask);
if (error != -EAGAIN)
return error;
}
if (in_group_p(inode->i_gid))
mode >>= 3;
}
/*
* If the DACs are ok we don't need any capability check.
*/
if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
return 0;
return -EACCES;
}
/**
* generic_permission - check for access rights on a Posix-like filesystem
* @inode: inode to check access rights for
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
*
* Used to check for read/write/execute permissions on a file.
* We use "fsuid" for this, letting us set arbitrary permissions
* for filesystem access without changing the "normal" uids which
* are used for other things.
*
* generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
* request cannot be satisfied (eg. requires blocking or too much complexity).
* It would then be called again in ref-walk mode.
*/
int generic_permission(struct inode *inode, int mask)
{
int ret;
/*
* Do the basic permission checks.
*/
ret = acl_permission_check(inode, mask);
if (ret != -EACCES)
return ret;
if (S_ISDIR(inode->i_mode)) {
/* DACs are overridable for directories */
if (inode_capable(inode, CAP_DAC_OVERRIDE))
return 0;
if (!(mask & MAY_WRITE))
if (inode_capable(inode, CAP_DAC_READ_SEARCH))
return 0;
return -EACCES;
}
/*
* Read/write DACs are always overridable.
* Executable DACs are overridable when there is
* at least one exec bit set.
*/
if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
if (inode_capable(inode, CAP_DAC_OVERRIDE))
return 0;
/*
* Searching includes executable on directories, else just read.
*/
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (mask == MAY_READ)
if (inode_capable(inode, CAP_DAC_READ_SEARCH))
return 0;
return -EACCES;
}
/*
* We _really_ want to just do "generic_permission()" without
* even looking at the inode->i_op values. So we keep a cache
* flag in inode->i_opflags, that says "this has not special
* permission function, use the fast case".
*/
static inline int do_inode_permission(struct inode *inode, int mask)
{
if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
if (likely(inode->i_op->permission))
return inode->i_op->permission(inode, mask);
/* This gets set once for the inode lifetime */
spin_lock(&inode->i_lock);
inode->i_opflags |= IOP_FASTPERM;
spin_unlock(&inode->i_lock);
}
return generic_permission(inode, mask);
}
/**
* __inode_permission - Check for access rights to a given inode
* @inode: Inode to check permission on
* @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
* Check for read/write/execute permissions on an inode.
*
* When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
*
* This does not check for a read-only file system. You probably want
* inode_permission().
*/
int __inode_permission(struct inode *inode, int mask)
{
int retval;
if (unlikely(mask & MAY_WRITE)) {
/*
* Nobody gets write access to an immutable file.
*/
if (IS_IMMUTABLE(inode))
return -EACCES;
}
retval = do_inode_permission(inode, mask);
if (retval)
return retval;
retval = devcgroup_inode_permission(inode, mask);
if (retval)
return retval;
return security_inode_permission(inode, mask);
}
/**
* sb_permission - Check superblock-level permissions
* @sb: Superblock of inode to check permission on
* @inode: Inode to check permission on
* @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
* Separate out file-system wide checks from inode-specific permission checks.
*/
static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
{
if (unlikely(mask & MAY_WRITE)) {
umode_t mode = inode->i_mode;
/* Nobody gets write access to a read-only fs. */
if ((sb->s_flags & MS_RDONLY) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
return -EROFS;
}
return 0;
}
/**
* inode_permission - Check for access rights to a given inode
* @inode: Inode to check permission on
* @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
* Check for read/write/execute permissions on an inode. We use fs[ug]id for
* this, letting us set arbitrary permissions for filesystem access without
* changing the "normal" UIDs which are used for other things.
*
* When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
*/
int inode_permission(struct inode *inode, int mask)
{
int retval;
retval = sb_permission(inode->i_sb, inode, mask);
if (retval)
return retval;
return __inode_permission(inode, mask);
}
/**
* path_get - get a reference to a path
* @path: path to get the reference to
*
* Given a path increment the reference count to the dentry and the vfsmount.
*/
void path_get(struct path *path)
{
mntget(path->mnt);
dget(path->dentry);
}
EXPORT_SYMBOL(path_get);
/**
* path_put - put a reference to a path
* @path: path to put the reference to
*
* Given a path decrement the reference count to the dentry and the vfsmount.
*/
void path_put(struct path *path)
{
dput(path->dentry);
mntput(path->mnt);
}
EXPORT_SYMBOL(path_put);
/*
* Path walking has 2 modes, rcu-walk and ref-walk (see
* Documentation/filesystems/path-lookup.txt). In situations when we can't
* continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
* normal reference counts on dentries and vfsmounts to transition to rcu-walk
* mode. Refcounts are grabbed at the last known good point before rcu-walk
* got stuck, so ref-walk may continue from there. If this is not successful
* (eg. a seqcount has changed), then failure is returned and it's up to caller
* to restart the path walk from the beginning in ref-walk mode.
*/
static inline void lock_rcu_walk(void)
{
br_read_lock(&vfsmount_lock);
rcu_read_lock();
}
static inline void unlock_rcu_walk(void)
{
rcu_read_unlock();
br_read_unlock(&vfsmount_lock);
}
/**
* unlazy_walk - try to switch to ref-walk mode.
* @nd: nameidata pathwalk data
* @dentry: child of nd->path.dentry or NULL
* Returns: 0 on success, -ECHILD on failure
*
* unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
* for ref-walk mode. @dentry must be a path found by a do_lookup call on
* @nd or NULL. Must be called from rcu-walk context.
*/
static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
{
struct fs_struct *fs = current->fs;
struct dentry *parent = nd->path.dentry;
int want_root = 0;
BUG_ON(!(nd->flags & LOOKUP_RCU));
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
want_root = 1;
spin_lock(&fs->lock);
if (nd->root.mnt != fs->root.mnt ||
nd->root.dentry != fs->root.dentry)
goto err_root;
}
spin_lock(&parent->d_lock);
if (!dentry) {
if (!__d_rcu_to_refcount(parent, nd->seq))
goto err_parent;
BUG_ON(nd->inode != parent->d_inode);
} else {
if (dentry->d_parent != parent)
goto err_parent;
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
if (!__d_rcu_to_refcount(dentry, nd->seq))
goto err_child;
/*
* If the sequence check on the child dentry passed, then
* the child has not been removed from its parent. This
* means the parent dentry must be valid and able to take
* a reference at this point.
*/
BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
BUG_ON(!parent->d_count);
parent->d_count++;
spin_unlock(&dentry->d_lock);
}
spin_unlock(&parent->d_lock);
if (want_root) {
path_get(&nd->root);
spin_unlock(&fs->lock);
}
mntget(nd->path.mnt);
unlock_rcu_walk();
nd->flags &= ~LOOKUP_RCU;
return 0;
err_child:
spin_unlock(&dentry->d_lock);
err_parent:
spin_unlock(&parent->d_lock);
err_root:
if (want_root)
spin_unlock(&fs->lock);
return -ECHILD;
}
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
return dentry->d_op->d_revalidate(dentry, flags);
}
/**
* complete_walk - successful completion of path walk
* @nd: pointer nameidata
*
* If we had been in RCU mode, drop out of it and legitimize nd->path.
* Revalidate the final result, unless we'd already done that during
* the path walk or the filesystem doesn't ask for it. Return 0 on
* success, -error on failure. In case of failure caller does not
* need to drop nd->path.
*/
static int complete_walk(struct nameidata *nd)
{
struct dentry *dentry = nd->path.dentry;
int status;
if (nd->flags & LOOKUP_RCU) {
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
spin_lock(&dentry->d_lock);
if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
spin_unlock(&dentry->d_lock);
unlock_rcu_walk();
return -ECHILD;
}
BUG_ON(nd->inode != dentry->d_inode);
spin_unlock(&dentry->d_lock);
mntget(nd->path.mnt);
unlock_rcu_walk();
}
if (likely(!(nd->flags & LOOKUP_JUMPED)))
return 0;
if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
return 0;
if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
return 0;
/* Note: we do not d_invalidate() */
status = d_revalidate(dentry, nd->flags);
if (status > 0)
return 0;
if (!status)
status = -ESTALE;
path_put(&nd->path);
return status;
}
static __always_inline void set_root(struct nameidata *nd)
{
if (!nd->root.mnt)
get_fs_root(current->fs, &nd->root);
}
static int link_path_walk(const char *, struct nameidata *);
static __always_inline void set_root_rcu(struct nameidata *nd)
{
if (!nd->root.mnt) {
struct fs_struct *fs = current->fs;
unsigned seq;
do {
seq = read_seqcount_begin(&fs->seq);
nd->root = fs->root;
nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
} while (read_seqcount_retry(&fs->seq, seq));
}
}
static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
{
int ret;
if (IS_ERR(link))
goto fail;
if (*link == '/') {
set_root(nd);
path_put(&nd->path);
nd->path = nd->root;
path_get(&nd->root);
nd->flags |= LOOKUP_JUMPED;
}
nd->inode = nd->path.dentry->d_inode;
ret = link_path_walk(link, nd);
return ret;
fail:
path_put(&nd->path);
return PTR_ERR(link);
}
static void path_put_conditional(struct path *path, struct nameidata *nd)
{
dput(path->dentry);
if (path->mnt != nd->path.mnt)
mntput(path->mnt);
}
static inline void path_to_nameidata(const struct path *path,
struct nameidata *nd)
{
if (!(nd->flags & LOOKUP_RCU)) {
dput(nd->path.dentry);
if (nd->path.mnt != path->mnt)
mntput(nd->path.mnt);
}
nd->path.mnt = path->mnt;
nd->path.dentry = path->dentry;
}
/*
* Helper to directly jump to a known parsed path from ->follow_link,
* caller must have taken a reference to path beforehand.
*/
void nd_jump_link(struct nameidata *nd, struct path *path)
{
path_put(&nd->path);
nd->path = *path;
nd->inode = nd->path.dentry->d_inode;
nd->flags |= LOOKUP_JUMPED;
BUG_ON(nd->inode->i_op->follow_link);
}
static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
{
struct inode *inode = link->dentry->d_inode;
if (inode->i_op->put_link)
inode->i_op->put_link(link->dentry, nd, cookie);
path_put(link);
}
int sysctl_protected_symlinks __read_mostly = 0;
int sysctl_protected_hardlinks __read_mostly = 0;
/**
* may_follow_link - Check symlink following for unsafe situations
* @link: The path of the symlink
* @nd: nameidata pathwalk data
*
* In the case of the sysctl_protected_symlinks sysctl being enabled,
* CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
* in a sticky world-writable directory. This is to protect privileged
* processes from failing races against path names that may change out
* from under them by way of other users creating malicious symlinks.
* It will permit symlinks to be followed only when outside a sticky
* world-writable directory, or when the uid of the symlink and follower
* match, or when the directory owner matches the symlink's owner.
*
* Returns 0 if following the symlink is allowed, -ve on error.
*/
static inline int may_follow_link(struct path *link, struct nameidata *nd)
{
const struct inode *inode;
const struct inode *parent;
if (!sysctl_protected_symlinks)
return 0;
/* Allowed if owner and follower match. */
inode = link->dentry->d_inode;
if (uid_eq(current_cred()->fsuid, inode->i_uid))
return 0;
/* Allowed if parent directory not sticky and world-writable. */
parent = nd->path.dentry->d_inode;
if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
return 0;
/* Allowed if parent directory and link owner match. */
if (uid_eq(parent->i_uid, inode->i_uid))
return 0;
audit_log_link_denied("follow_link", link);
path_put_conditional(link, nd);
path_put(&nd->path);
return -EACCES;
}
/**
* safe_hardlink_source - Check for safe hardlink conditions
* @inode: the source inode to hardlink from
*
* Return false if at least one of the following conditions:
* - inode is not a regular file
* - inode is setuid
* - inode is setgid and group-exec
* - access failure for read and write
*
* Otherwise returns true.
*/
static bool safe_hardlink_source(struct inode *inode)
{
umode_t mode = inode->i_mode;
/* Special files should not get pinned to the filesystem. */
if (!S_ISREG(mode))
return false;
/* Setuid files should not get pinned to the filesystem. */
if (mode & S_ISUID)
return false;
/* Executable setgid files should not get pinned to the filesystem. */
if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
return false;
/* Hardlinking to unreadable or unwritable sources is dangerous. */
if (inode_permission(inode, MAY_READ | MAY_WRITE))
return false;
return true;
}
/**
* may_linkat - Check permissions for creating a hardlink
* @link: the source to hardlink from
*
* Block hardlink when all of:
* - sysctl_protected_hardlinks enabled
* - fsuid does not match inode
* - hardlink source is unsafe (see safe_hardlink_source() above)
* - not CAP_FOWNER
*
* Returns 0 if successful, -ve on error.
*/
static int may_linkat(struct path *link)
{
const struct cred *cred;
struct inode *inode;
if (!sysctl_protected_hardlinks)
return 0;
cred = current_cred();
inode = link->dentry->d_inode;
/* Source inode owner (or CAP_FOWNER) can hardlink all they like,
* otherwise, it must be a safe source.
*/
if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
capable(CAP_FOWNER))
return 0;
audit_log_link_denied("linkat", link);
return -EPERM;
}
static __always_inline int
follow_link(struct path *link, struct nameidata *nd, void **p)
{
struct dentry *dentry = link->dentry;
int error;
char *s;
BUG_ON(nd->flags & LOOKUP_RCU);
if (link->mnt == nd->path.mnt)
mntget(link->mnt);
error = -ELOOP;
if (unlikely(current->total_link_count >= 40))
goto out_put_nd_path;
cond_resched();
current->total_link_count++;
touch_atime(link);
nd_set_link(nd, NULL);
error = security_inode_follow_link(link->dentry, nd);
if (error)
goto out_put_nd_path;
nd->last_type = LAST_BIND;
*p = dentry->d_inode->i_op->follow_link(dentry, nd);
error = PTR_ERR(*p);
if (IS_ERR(*p))
goto out_put_nd_path;
error = 0;
s = nd_get_link(nd);
if (s) {
error = __vfs_follow_link(nd, s);
if (unlikely(error))
put_link(nd, link, *p);
}
return error;
out_put_nd_path:
*p = NULL;
path_put(&nd->path);
path_put(link);
return error;
}
static int follow_up_rcu(struct path *path)
{
struct mount *mnt = real_mount(path->mnt);
struct mount *parent;
struct dentry *mountpoint;
parent = mnt->mnt_parent;
if (&parent->mnt == path->mnt)
return 0;
mountpoint = mnt->mnt_mountpoint;
path->dentry = mountpoint;
path->mnt = &parent->mnt;
return 1;
}
/*
* follow_up - Find the mountpoint of path's vfsmount
*
* Given a path, find the mountpoint of its source file system.
* Replace @path with the path of the mountpoint in the parent mount.
* Up is towards /.
*
* Return 1 if we went up a level and 0 if we were already at the
* root.
*/
int follow_up(struct path *path)
{
struct mount *mnt = real_mount(path->mnt);
struct mount *parent;
struct dentry *mountpoint;
br_read_lock(&vfsmount_lock);
parent = mnt->mnt_parent;
if (parent == mnt) {
br_read_unlock(&vfsmount_lock);
return 0;
}
mntget(&parent->mnt);
mountpoint = dget(mnt->mnt_mountpoint);
br_read_unlock(&vfsmount_lock);
dput(path->dentry);
path->dentry = mountpoint;
mntput(path->mnt);
path->mnt = &parent->mnt;
return 1;
}
/*
* Perform an automount
* - return -EISDIR to tell follow_managed() to stop and return the path we
* were called with.
*/
static int follow_automount(struct path *path, unsigned flags,
bool *need_mntput)
{
struct vfsmount *mnt;
int err;
if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
return -EREMOTE;
/* We don't want to mount if someone's just doing a stat -
* unless they're stat'ing a directory and appended a '/' to
* the name.
*
* We do, however, want to mount if someone wants to open or
* create a file of any type under the mountpoint, wants to
* traverse through the mountpoint or wants to open the
* mounted directory. Also, autofs may mark negative dentries
* as being automount points. These will need the attentions
* of the daemon to instantiate them before they can be used.
*/
if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
path->dentry->d_inode)
return -EISDIR;
current->total_link_count++;
if (current->total_link_count >= 40)
return -ELOOP;
mnt = path->dentry->d_op->d_automount(path);
if (IS_ERR(mnt)) {
/*
* The filesystem is allowed to return -EISDIR here to indicate
* it doesn't want to automount. For instance, autofs would do
* this so that its userspace daemon can mount on this dentry.
*
* However, we can only permit this if it's a terminal point in
* the path being looked up; if it wasn't then the remainder of
* the path is inaccessible and we should say so.
*/
if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
return -EREMOTE;
return PTR_ERR(mnt);
}
if (!mnt) /* mount collision */
return 0;
if (!*need_mntput) {
/* lock_mount() may release path->mnt on error */
mntget(path->mnt);
*need_mntput = true;
}
err = finish_automount(mnt, path);
switch (err) {
case -EBUSY:
/* Someone else made a mount here whilst we were busy */
return 0;
case 0:
path_put(path);
path->mnt = mnt;
path->dentry = dget(mnt->mnt_root);
return 0;
default:
return err;
}
}
/*
* Handle a dentry that is managed in some way.
* - Flagged for transit management (autofs)
* - Flagged as mountpoint
* - Flagged as automount point
*
* This may only be called in refwalk mode.
*
* Serialization is taken care of in namespace.c
*/
static int follow_managed(struct path *path, unsigned flags)
{
struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
unsigned managed;
bool need_mntput = false;
int ret = 0;
/* Given that we're not holding a lock here, we retain the value in a
* local variable for each dentry as we look at it so that we don't see
* the components of that value change under us */
while (managed = ACCESS_ONCE(path->dentry->d_flags),
managed &= DCACHE_MANAGED_DENTRY,
unlikely(managed != 0)) {
/* Allow the filesystem to manage the transit without i_mutex
* being held. */
if (managed & DCACHE_MANAGE_TRANSIT) {
BUG_ON(!path->dentry->d_op);
BUG_ON(!path->dentry->d_op->d_manage);
ret = path->dentry->d_op->d_manage(path->dentry, false);
if (ret < 0)
break;
}
/* Transit to a mounted filesystem. */
if (managed & DCACHE_MOUNTED) {
struct vfsmount *mounted = lookup_mnt(path);
if (mounted) {
dput(path->dentry);
if (need_mntput)
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
need_mntput = true;
continue;
}
/* Something is mounted on this dentry in another
* namespace and/or whatever was mounted there in this
* namespace got unmounted before we managed to get the
* vfsmount_lock */
}
/* Handle an automount point */
if (managed & DCACHE_NEED_AUTOMOUNT) {
ret = follow_automount(path, flags, &need_mntput);
if (ret < 0)
break;
continue;
}
/* We didn't change the current path point */
break;
}
if (need_mntput && path->mnt == mnt)
mntput(path->mnt);
if (ret == -EISDIR)
ret = 0;
return ret < 0 ? ret : need_mntput;
}
int follow_down_one(struct path *path)
{
struct vfsmount *mounted;
mounted = lookup_mnt(path);
if (mounted) {
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
return 1;
}
return 0;
}
static inline bool managed_dentry_might_block(struct dentry *dentry)
{
return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
dentry->d_op->d_manage(dentry, true) < 0);
}
/*
* Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
* we meet a managed dentry that would need blocking.
*/
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode)
{
for (;;) {
struct mount *mounted;
/*
* Don't forget we might have a non-mountpoint managed dentry
* that wants to block transit.
*/
if (unlikely(managed_dentry_might_block(path->dentry)))
return false;
if (!d_mountpoint(path->dentry))
break;
mounted = __lookup_mnt(path->mnt, path->dentry, 1);
if (!mounted)
break;
path->mnt = &mounted->mnt;
path->dentry = mounted->mnt.mnt_root;
nd->flags |= LOOKUP_JUMPED;
nd->seq = read_seqcount_begin(&path->dentry->d_seq);
/*
* Update the inode too. We don't need to re-check the
* dentry sequence number here after this d_inode read,
* because a mount-point is always pinned.
*/
*inode = path->dentry->d_inode;
}
return true;
}
static void follow_mount_rcu(struct nameidata *nd)
{
while (d_mountpoint(nd->path.dentry)) {
struct mount *mounted;
mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
if (!mounted)
break;
nd->path.mnt = &mounted->mnt;
nd->path.dentry = mounted->mnt.mnt_root;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
}
}
static int follow_dotdot_rcu(struct nameidata *nd)
{
set_root_rcu(nd);
while (1) {
if (nd->path.dentry == nd->root.dentry &&
nd->path.mnt == nd->root.mnt) {
break;
}
if (nd->path.dentry != nd->path.mnt->mnt_root) {
struct dentry *old = nd->path.dentry;
struct dentry *parent = old->d_parent;
unsigned seq;
seq = read_seqcount_begin(&parent->d_seq);
if (read_seqcount_retry(&old->d_seq, nd->seq))
goto failed;
nd->path.dentry = parent;
nd->seq = seq;
break;
}
if (!follow_up_rcu(&nd->path))
break;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
}
follow_mount_rcu(nd);
nd->inode = nd->path.dentry->d_inode;
return 0;
failed:
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
unlock_rcu_walk();
return -ECHILD;
}
/*
* Follow down to the covering mount currently visible to userspace. At each
* point, the filesystem owning that dentry may be queried as to whether the
* caller is permitted to proceed or not.
*/
int follow_down(struct path *path)
{
unsigned managed;
int ret;
while (managed = ACCESS_ONCE(path->dentry->d_flags),
unlikely(managed & DCACHE_MANAGED_DENTRY)) {
/* Allow the filesystem to manage the transit without i_mutex
* being held.
*
* We indicate to the filesystem if someone is trying to mount
* something here. This gives autofs the chance to deny anyone
* other than its daemon the right to mount on its
* superstructure.
*
* The filesystem may sleep at this point.
*/
if (managed & DCACHE_MANAGE_TRANSIT) {
BUG_ON(!path->dentry->d_op);
BUG_ON(!path->dentry->d_op->d_manage);
ret = path->dentry->d_op->d_manage(
path->dentry, false);
if (ret < 0)
return ret == -EISDIR ? 0 : ret;
}
/* Transit to a mounted filesystem. */
if (managed & DCACHE_MOUNTED) {
struct vfsmount *mounted = lookup_mnt(path);
if (!mounted)
break;
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
continue;
}
/* Don't handle automount points here */
break;
}
return 0;
}
/*
* Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
*/
static void follow_mount(struct path *path)
{
while (d_mountpoint(path->dentry)) {
struct vfsmount *mounted = lookup_mnt(path);
if (!mounted)
break;
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
}
}
static void follow_dotdot(struct nameidata *nd)
{
set_root(nd);
while(1) {
struct dentry *old = nd->path.dentry;
if (nd->path.dentry == nd->root.dentry &&
nd->path.mnt == nd->root.mnt) {
break;
}
if (nd->path.dentry != nd->path.mnt->mnt_root) {
/* rare case of legitimate dget_parent()... */
nd->path.dentry = dget_parent(nd->path.dentry);
dput(old);
break;
}
if (!follow_up(&nd->path))
break;
}
follow_mount(&nd->path);
nd->inode = nd->path.dentry->d_inode;
}
/*
* This looks up the name in dcache, possibly revalidates the old dentry and
* allocates a new one if not found or not valid. In the need_lookup argument
* returns whether i_op->lookup is necessary.
*
* dir->d_inode->i_mutex must be held
*/
static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
unsigned int flags, bool *need_lookup)
{
struct dentry *dentry;
int error;
*need_lookup = false;
dentry = d_lookup(dir, name);
if (dentry) {
if (d_need_lookup(dentry)) {
*need_lookup = true;
} else if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
error = d_revalidate(dentry, flags);
if (unlikely(error <= 0)) {
if (error < 0) {
dput(dentry);
return ERR_PTR(error);
} else if (!d_invalidate(dentry)) {
dput(dentry);
dentry = NULL;
}
}
}
}
if (!dentry) {
dentry = d_alloc(dir, name);
if (unlikely(!dentry))
return ERR_PTR(-ENOMEM);
*need_lookup = true;
}
return dentry;
}
/*
* Call i_op->lookup on the dentry. The dentry must be negative but may be
* hashed if it was pouplated with DCACHE_NEED_LOOKUP.
*
* dir->d_inode->i_mutex must be held
*/
static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct dentry *old;
/* Don't create child dentry for a dead directory. */
if (unlikely(IS_DEADDIR(dir))) {
dput(dentry);
return ERR_PTR(-ENOENT);
}
old = dir->i_op->lookup(dir, dentry, flags);
if (unlikely(old)) {
dput(dentry);
dentry = old;
}
return dentry;
}
static struct dentry *__lookup_hash(struct qstr *name,
struct dentry *base, unsigned int flags)
{
bool need_lookup;
struct dentry *dentry;
dentry = lookup_dcache(name, base, flags, &need_lookup);
if (!need_lookup)
return dentry;
return lookup_real(base->d_inode, dentry, flags);
}
/*
* It's more convoluted than I'd like it to be, but... it's still fairly
* small and for now I'd prefer to have fast path as straight as possible.
* It _is_ time-critical.
*/
static int lookup_fast(struct nameidata *nd, struct qstr *name,
struct path *path, struct inode **inode)
{
struct vfsmount *mnt = nd->path.mnt;
struct dentry *dentry, *parent = nd->path.dentry;
int need_reval = 1;
int status = 1;
int err;
/*
* Rename seqlock is not required here because in the off chance
* of a false negative due to a concurrent rename, we're going to
* do the non-racy lookup, below.
*/
if (nd->flags & LOOKUP_RCU) {
unsigned seq;
dentry = __d_lookup_rcu(parent, name, &seq, nd->inode);
if (!dentry)
goto unlazy;
/*
* This sequence count validates that the inode matches
* the dentry name information from lookup.
*/
*inode = dentry->d_inode;
if (read_seqcount_retry(&dentry->d_seq, seq))
return -ECHILD;
/*
* This sequence count validates that the parent had no
* changes while we did the lookup of the dentry above.
*
* The memory barrier in read_seqcount_begin of child is
* enough, we can use __read_seqcount_retry here.
*/
if (__read_seqcount_retry(&parent->d_seq, nd->seq))
return -ECHILD;
nd->seq = seq;
if (unlikely(d_need_lookup(dentry)))
goto unlazy;
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
status = d_revalidate(dentry, nd->flags);
if (unlikely(status <= 0)) {
if (status != -ECHILD)
need_reval = 0;
goto unlazy;
}
}
path->mnt = mnt;
path->dentry = dentry;
if (unlikely(!__follow_mount_rcu(nd, path, inode)))
goto unlazy;
if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
goto unlazy;
return 0;
unlazy:
if (unlazy_walk(nd, dentry))
return -ECHILD;
} else {
dentry = __d_lookup(parent, name);
}
if (unlikely(!dentry))
goto need_lookup;
if (unlikely(d_need_lookup(dentry))) {
dput(dentry);
goto need_lookup;
}
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
status = d_revalidate(dentry, nd->flags);
if (unlikely(status <= 0)) {
if (status < 0) {
dput(dentry);
return status;
}
if (!d_invalidate(dentry)) {
dput(dentry);
goto need_lookup;
}
}
path->mnt = mnt;
path->dentry = dentry;
err = follow_managed(path, nd->flags);
if (unlikely(err < 0)) {
path_put_conditional(path, nd);
return err;
}
if (err)
nd->flags |= LOOKUP_JUMPED;
*inode = path->dentry->d_inode;
return 0;
need_lookup:
return 1;
}
/* Fast lookup failed, do it the slow way */
static int lookup_slow(struct nameidata *nd, struct qstr *name,
struct path *path)
{
struct dentry *dentry, *parent;
int err;
parent = nd->path.dentry;
BUG_ON(nd->inode != parent->d_inode);
mutex_lock(&parent->d_inode->i_mutex);
dentry = __lookup_hash(name, parent, nd->flags);
mutex_unlock(&parent->d_inode->i_mutex);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
path->mnt = nd->path.mnt;
path->dentry = dentry;
err = follow_managed(path, nd->flags);
if (unlikely(err < 0)) {
path_put_conditional(path, nd);
return err;
}
if (err)
nd->flags |= LOOKUP_JUMPED;
return 0;
}
static inline int may_lookup(struct nameidata *nd)
{
if (nd->flags & LOOKUP_RCU) {
int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
if (err != -ECHILD)
return err;
if (unlazy_walk(nd, NULL))
return -ECHILD;
}
return inode_permission(nd->inode, MAY_EXEC);
}
static inline int handle_dots(struct nameidata *nd, int type)
{
if (type == LAST_DOTDOT) {
if (nd->flags & LOOKUP_RCU) {
if (follow_dotdot_rcu(nd))
return -ECHILD;
} else
follow_dotdot(nd);
}
return 0;
}
static void terminate_walk(struct nameidata *nd)
{
if (!(nd->flags & LOOKUP_RCU)) {
path_put(&nd->path);
} else {
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
unlock_rcu_walk();
}
}
/*
* Do we need to follow links? We _really_ want to be able
* to do this check without having to look at inode->i_op,
* so we keep a cache of "no, this doesn't need follow_link"
* for the common case.
*/
static inline int should_follow_link(struct inode *inode, int follow)
{
if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
if (likely(inode->i_op->follow_link))
return follow;
/* This gets set once for the inode lifetime */
spin_lock(&inode->i_lock);
inode->i_opflags |= IOP_NOFOLLOW;
spin_unlock(&inode->i_lock);
}
return 0;
}
static inline int walk_component(struct nameidata *nd, struct path *path,
struct qstr *name, int type, int follow)
{
struct inode *inode;
int err;
/*
* "." and ".." are special - ".." especially so because it has
* to be able to know about the current root directory and
* parent relationships.
*/
if (unlikely(type != LAST_NORM))
return handle_dots(nd, type);
err = lookup_fast(nd, name, path, &inode);
if (unlikely(err)) {
if (err < 0)
goto out_err;
err = lookup_slow(nd, name, path);
if (err < 0)
goto out_err;
inode = path->dentry->d_inode;
}
err = -ENOENT;
if (!inode)
goto out_path_put;
if (should_follow_link(inode, follow)) {
if (nd->flags & LOOKUP_RCU) {
if (unlikely(unlazy_walk(nd, path->dentry))) {
err = -ECHILD;
goto out_err;
}
}
BUG_ON(inode != path->dentry->d_inode);
return 1;
}
path_to_nameidata(path, nd);
nd->inode = inode;
return 0;
out_path_put:
path_to_nameidata(path, nd);
out_err:
terminate_walk(nd);
return err;
}
/*
* This limits recursive symlink follows to 8, while
* limiting consecutive symlinks to 40.
*
* Without that kind of total limit, nasty chains of consecutive
* symlinks can cause almost arbitrarily long lookups.
*/
static inline int nested_symlink(struct path *path, struct nameidata *nd)
{
int res;
if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
path_put_conditional(path, nd);
path_put(&nd->path);
return -ELOOP;
}
BUG_ON(nd->depth >= MAX_NESTED_LINKS);
nd->depth++;
current->link_count++;
do {
struct path link = *path;
void *cookie;
res = follow_link(&link, nd, &cookie);
if (res)
break;
res = walk_component(nd, path, &nd->last,
nd->last_type, LOOKUP_FOLLOW);
put_link(nd, &link, cookie);
} while (res > 0);
current->link_count--;
nd->depth--;
return res;
}
/*
* We really don't want to look at inode->i_op->lookup
* when we don't have to. So we keep a cache bit in
* the inode ->i_opflags field that says "yes, we can
* do lookup on this inode".
*/
static inline int can_lookup(struct inode *inode)
{
if (likely(inode->i_opflags & IOP_LOOKUP))
return 1;
if (likely(!inode->i_op->lookup))
return 0;
/* We do this once for the lifetime of the inode */
spin_lock(&inode->i_lock);
inode->i_opflags |= IOP_LOOKUP;
spin_unlock(&inode->i_lock);
return 1;
}
/*
* We can do the critical dentry name comparison and hashing
* operations one word at a time, but we are limited to:
*
* - Architectures with fast unaligned word accesses. We could
* do a "get_unaligned()" if this helps and is sufficiently
* fast.
*
* - Little-endian machines (so that we can generate the mask
* of low bytes efficiently). Again, we *could* do a byte
* swapping load on big-endian architectures if that is not
* expensive enough to make the optimization worthless.
*
* - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
* do not trap on the (extremely unlikely) case of a page
* crossing operation.
*
* - Furthermore, we need an efficient 64-bit compile for the
* 64-bit case in order to generate the "number of bytes in
* the final mask". Again, that could be replaced with a
* efficient population count instruction or similar.
*/
#ifdef CONFIG_DCACHE_WORD_ACCESS
#include <asm/word-at-a-time.h>
#ifdef CONFIG_64BIT
static inline unsigned int fold_hash(unsigned long hash)
{
hash += hash >> (8*sizeof(int));
return hash;
}
#else /* 32-bit case */
#define fold_hash(x) (x)
#endif
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
{
unsigned long a, mask;
unsigned long hash = 0;
for (;;) {
a = load_unaligned_zeropad(name);
if (len < sizeof(unsigned long))
break;
hash += a;
hash *= 9;
name += sizeof(unsigned long);
len -= sizeof(unsigned long);
if (!len)
goto done;
}
mask = ~(~0ul << len*8);
hash += mask & a;
done:
return fold_hash(hash);
}
EXPORT_SYMBOL(full_name_hash);
/*
* Calculate the length and hash of the path component, and
* return the length of the component;
*/
static inline unsigned long hash_name(const char *name, unsigned int *hashp)
{
unsigned long a, b, adata, bdata, mask, hash, len;
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
hash = a = 0;
len = -sizeof(unsigned long);
do {
hash = (hash + a) * 9;
len += sizeof(unsigned long);
a = load_unaligned_zeropad(name+len);
b = a ^ REPEAT_BYTE('/');
} while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
adata = prep_zero_mask(a, adata, &constants);
bdata = prep_zero_mask(b, bdata, &constants);
mask = create_zero_mask(adata | bdata);
hash += a & zero_bytemask(mask);
*hashp = fold_hash(hash);
return len + find_zero(mask);
}
#else
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
{
unsigned long hash = init_name_hash();
while (len--)
hash = partial_name_hash(*name++, hash);
return end_name_hash(hash);
}
EXPORT_SYMBOL(full_name_hash);
/*
* We know there's a real path component here of at least
* one character.
*/
static inline unsigned long hash_name(const char *name, unsigned int *hashp)
{
unsigned long hash = init_name_hash();
unsigned long len = 0, c;
c = (unsigned char)*name;
do {
len++;
hash = partial_name_hash(c, hash);
c = (unsigned char)name[len];
} while (c && c != '/');
*hashp = end_name_hash(hash);
return len;
}
#endif
/*
* Name resolution.
* This is the basic name resolution function, turning a pathname into
* the final dentry. We expect 'base' to be positive and a directory.
*
* Returns 0 and nd will have valid dentry and mnt on success.
* Returns error and drops reference to input namei data on failure.
*/
static int link_path_walk(const char *name, struct nameidata *nd)
{
struct path next;
int err;
while (*name=='/')
name++;
if (!*name)
return 0;
/* At this point we know we have a real path component. */
for(;;) {
struct qstr this;
long len;
int type;
err = may_lookup(nd);
if (err)
break;
len = hash_name(name, &this.hash);
this.name = name;
this.len = len;
type = LAST_NORM;
if (name[0] == '.') switch (len) {
case 2:
if (name[1] == '.') {
type = LAST_DOTDOT;
nd->flags |= LOOKUP_JUMPED;
}
break;
case 1:
type = LAST_DOT;
}
if (likely(type == LAST_NORM)) {
struct dentry *parent = nd->path.dentry;
nd->flags &= ~LOOKUP_JUMPED;
if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
err = parent->d_op->d_hash(parent, nd->inode,
&this);
if (err < 0)
break;
}
}
if (!name[len])
goto last_component;
/*
* If it wasn't NUL, we know it was '/'. Skip that
* slash, and continue until no more slashes.
*/
do {
len++;
} while (unlikely(name[len] == '/'));
if (!name[len])
goto last_component;
name += len;
err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
if (err < 0)
return err;
if (err) {
err = nested_symlink(&next, nd);
if (err)
return err;
}
if (can_lookup(nd->inode))
continue;
err = -ENOTDIR;
break;
/* here ends the main loop */
last_component:
nd->last = this;
nd->last_type = type;
return 0;
}
terminate_walk(nd);
return err;
}
static int path_init(int dfd, const char *name, unsigned int flags,
struct nameidata *nd, struct file **fp)
{
int retval = 0;
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags | LOOKUP_JUMPED;
nd->depth = 0;
if (flags & LOOKUP_ROOT) {
struct inode *inode = nd->root.dentry->d_inode;
if (*name) {
if (!inode->i_op->lookup)
return -ENOTDIR;
retval = inode_permission(inode, MAY_EXEC);
if (retval)
return retval;
}
nd->path = nd->root;
nd->inode = inode;
if (flags & LOOKUP_RCU) {
lock_rcu_walk();
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
} else {
path_get(&nd->path);
}
return 0;
}
nd->root.mnt = NULL;
if (*name=='/') {
if (flags & LOOKUP_RCU) {
lock_rcu_walk();
set_root_rcu(nd);
} else {
set_root(nd);
path_get(&nd->root);
}
nd->path = nd->root;
} else if (dfd == AT_FDCWD) {
if (flags & LOOKUP_RCU) {
struct fs_struct *fs = current->fs;
unsigned seq;
lock_rcu_walk();
do {
seq = read_seqcount_begin(&fs->seq);
nd->path = fs->pwd;
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
} while (read_seqcount_retry(&fs->seq, seq));
} else {
get_fs_pwd(current->fs, &nd->path);
}
} else {
struct fd f = fdget_raw(dfd);
struct dentry *dentry;
if (!f.file)
return -EBADF;
dentry = f.file->f_path.dentry;
if (*name) {
if (!S_ISDIR(dentry->d_inode->i_mode)) {
fdput(f);
return -ENOTDIR;
}
retval = inode_permission(dentry->d_inode, MAY_EXEC);
if (retval) {
fdput(f);
return retval;
}
}
nd->path = f.file->f_path;
if (flags & LOOKUP_RCU) {
if (f.need_put)
*fp = f.file;
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
lock_rcu_walk();
} else {
path_get(&nd->path);
fdput(f);
}
}
nd->inode = nd->path.dentry->d_inode;
return 0;
}
static inline int lookup_last(struct nameidata *nd, struct path *path)
{
if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
nd->flags &= ~LOOKUP_PARENT;
return walk_component(nd, path, &nd->last, nd->last_type,
nd->flags & LOOKUP_FOLLOW);
}
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
static int path_lookupat(int dfd, const char *name,
unsigned int flags, struct nameidata *nd)
{
struct file *base = NULL;
struct path path;
int err;
/*
* Path walking is largely split up into 2 different synchronisation
* schemes, rcu-walk and ref-walk (explained in
* Documentation/filesystems/path-lookup.txt). These share much of the
* path walk code, but some things particularly setup, cleanup, and
* following mounts are sufficiently divergent that functions are
* duplicated. Typically there is a function foo(), and its RCU
* analogue, foo_rcu().
*
* -ECHILD is the error number of choice (just to avoid clashes) that
* is returned if some aspect of an rcu-walk fails. Such an error must
* be handled by restarting a traditional ref-walk (which will always
* be able to complete).
*/
err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
if (unlikely(err))
return err;
current->total_link_count = 0;
err = link_path_walk(name, nd);
if (!err && !(flags & LOOKUP_PARENT)) {
err = lookup_last(nd, &path);
while (err > 0) {
void *cookie;
struct path link = path;
err = may_follow_link(&link, nd);
if (unlikely(err))
break;
nd->flags |= LOOKUP_PARENT;
err = follow_link(&link, nd, &cookie);
if (err)
break;
err = lookup_last(nd, &path);
put_link(nd, &link, cookie);
}
}
if (!err)
err = complete_walk(nd);
if (!err && nd->flags & LOOKUP_DIRECTORY) {
if (!nd->inode->i_op->lookup) {
path_put(&nd->path);
err = -ENOTDIR;
}
}
if (base)
fput(base);
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
path_put(&nd->root);
nd->root.mnt = NULL;
}
return err;
}
static int filename_lookup(int dfd, struct filename *name,
unsigned int flags, struct nameidata *nd)
{
int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
if (unlikely(retval == -ECHILD))
retval = path_lookupat(dfd, name->name, flags, nd);
if (unlikely(retval == -ESTALE))
retval = path_lookupat(dfd, name->name,
flags | LOOKUP_REVAL, nd);
if (likely(!retval))
audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
return retval;
}
static int do_path_lookup(int dfd, const char *name,
unsigned int flags, struct nameidata *nd)
{
struct filename filename = { .name = name };
return filename_lookup(dfd, &filename, flags, nd);
}
/* does lookup, returns the object with parent locked */
struct dentry *kern_path_locked(const char *name, struct path *path)
{
struct nameidata nd;
struct dentry *d;
int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd);
if (err)
return ERR_PTR(err);
if (nd.last_type != LAST_NORM) {
path_put(&nd.path);
return ERR_PTR(-EINVAL);
}
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
d = __lookup_hash(&nd.last, nd.path.dentry, 0);
if (IS_ERR(d)) {
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
path_put(&nd.path);
return d;
}
*path = nd.path;
return d;
}
int kern_path(const char *name, unsigned int flags, struct path *path)
{
struct nameidata nd;
int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
if (!res)
*path = nd.path;
return res;
}
/**
* vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
* @dentry: pointer to dentry of the base directory
* @mnt: pointer to vfs mount of the base directory
* @name: pointer to file name
* @flags: lookup flags
* @path: pointer to struct path to fill
*/
int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
const char *name, unsigned int flags,
struct path *path)
{
struct nameidata nd;
int err;
nd.root.dentry = dentry;
nd.root.mnt = mnt;
BUG_ON(flags & LOOKUP_PARENT);
/* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
if (!err)
*path = nd.path;
return err;
}
/*
* Restricted form of lookup. Doesn't follow links, single-component only,
* needs parent already locked. Doesn't follow mounts.
* SMP-safe.
*/
static struct dentry *lookup_hash(struct nameidata *nd)
{
return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
}
/**
* lookup_one_len - filesystem helper to lookup single pathname component
* @name: pathname component to lookup
* @base: base directory to lookup from
* @len: maximum length @len should be interpreted to
*
* Note that this routine is purely a helper for filesystem usage and should
* not be called by generic code. Also note that by using this function the
* nameidata argument is passed to the filesystem methods and a filesystem
* using this helper needs to be prepared for that.
*/
struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
{
struct qstr this;
unsigned int c;
int err;
WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
this.name = name;
this.len = len;
this.hash = full_name_hash(name, len);
if (!len)
return ERR_PTR(-EACCES);
while (len--) {
c = *(const unsigned char *)name++;
if (c == '/' || c == '\0')
return ERR_PTR(-EACCES);
}
/*
* See if the low-level filesystem might want
* to use its own hash..
*/
if (base->d_flags & DCACHE_OP_HASH) {
int err = base->d_op->d_hash(base, base->d_inode, &this);
if (err < 0)
return ERR_PTR(err);
}
err = inode_permission(base->d_inode, MAY_EXEC);
if (err)
return ERR_PTR(err);
return __lookup_hash(&this, base, 0);
}
int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
struct path *path, int *empty)
{
struct nameidata nd;
struct filename *tmp = getname_flags(name, flags, empty);
int err = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
BUG_ON(flags & LOOKUP_PARENT);
err = filename_lookup(dfd, tmp, flags, &nd);
putname(tmp);
if (!err)
*path = nd.path;
}
return err;
}
int user_path_at(int dfd, const char __user *name, unsigned flags,
struct path *path)
{
return user_path_at_empty(dfd, name, flags, path, NULL);
}
/*
* NB: most callers don't do anything directly with the reference to the
* to struct filename, but the nd->last pointer points into the name string
* allocated by getname. So we must hold the reference to it until all
* path-walking is complete.
*/
static struct filename *
user_path_parent(int dfd, const char __user *path, struct nameidata *nd)
{
struct filename *s = getname(path);
int error;
if (IS_ERR(s))
return s;
error = filename_lookup(dfd, s, LOOKUP_PARENT, nd);
if (error) {
putname(s);
return ERR_PTR(error);
}
return s;
}
/*
* It's inline, so penalty for filesystems that don't use sticky bit is
* minimal.
*/
static inline int check_sticky(struct inode *dir, struct inode *inode)
{
kuid_t fsuid = current_fsuid();
if (!(dir->i_mode & S_ISVTX))
return 0;
if (uid_eq(inode->i_uid, fsuid))
return 0;
if (uid_eq(dir->i_uid, fsuid))
return 0;
return !inode_capable(inode, CAP_FOWNER);
}
/*
* Check whether we can remove a link victim from directory dir, check
* whether the type of victim is right.
* 1. We can't do it if dir is read-only (done in permission())
* 2. We should have write and exec permissions on dir
* 3. We can't remove anything from append-only dir
* 4. We can't do anything with immutable dir (done in permission())
* 5. If the sticky bit on dir is set we should either
* a. be owner of dir, or
* b. be owner of victim, or
* c. have CAP_FOWNER capability
* 6. If the victim is append-only or immutable we can't do antyhing with
* links pointing to it.
* 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
* 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
* 9. We can't remove a root or mountpoint.
* 10. We don't allow removal of NFS sillyrenamed files; it's handled by
* nfs_async_unlink().
*/
static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
{
int error;
if (!victim->d_inode)
return -ENOENT;
BUG_ON(victim->d_parent->d_inode != dir);
audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
if (error)
return error;
if (IS_APPEND(dir))
return -EPERM;
if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
return -EPERM;
if (isdir) {
if (!S_ISDIR(victim->d_inode->i_mode))
return -ENOTDIR;
if (IS_ROOT(victim))
return -EBUSY;
} else if (S_ISDIR(victim->d_inode->i_mode))
return -EISDIR;
if (IS_DEADDIR(dir))
return -ENOENT;
if (victim->d_flags & DCACHE_NFSFS_RENAMED)
return -EBUSY;
return 0;
}
/* Check whether we can create an object with dentry child in directory
* dir.
* 1. We can't do it if child already exists (open has special treatment for
* this case, but since we are inlined it's OK)
* 2. We can't do it if dir is read-only (done in permission())
* 3. We should have write and exec permissions on dir
* 4. We can't do it if dir is immutable (done in permission())
*/
static inline int may_create(struct inode *dir, struct dentry *child)
{
if (child->d_inode)
return -EEXIST;
if (IS_DEADDIR(dir))
return -ENOENT;
return inode_permission(dir, MAY_WRITE | MAY_EXEC);
}
/*
* p1 and p2 should be directories on the same fs.
*/
struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;
if (p1 == p2) {
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
return NULL;
}
mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
p = d_ancestor(p2, p1);
if (p) {
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
return p;
}
p = d_ancestor(p1, p2);
if (p) {
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
return p;
}
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
return NULL;
}
void unlock_rename(struct dentry *p1, struct dentry *p2)
{
mutex_unlock(&p1->d_inode->i_mutex);
if (p1 != p2) {
mutex_unlock(&p2->d_inode->i_mutex);
mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
}
}
int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
bool want_excl)
{
int error = may_create(dir, dentry);
if (error)
return error;
if (!dir->i_op->create)
return -EACCES; /* shouldn't it be ENOSYS? */
mode &= S_IALLUGO;
mode |= S_IFREG;
error = security_inode_create(dir, dentry, mode);
if (error)
return error;
error = dir->i_op->create(dir, dentry, mode, want_excl);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
static int may_open(struct path *path, int acc_mode, int flag)
{
struct dentry *dentry = path->dentry;
struct inode *inode = dentry->d_inode;
int error;
/* O_PATH? */
if (!acc_mode)
return 0;
if (!inode)
return -ENOENT;
switch (inode->i_mode & S_IFMT) {
case S_IFLNK:
return -ELOOP;
case S_IFDIR:
if (acc_mode & MAY_WRITE)
return -EISDIR;
break;
case S_IFBLK:
case S_IFCHR:
if (path->mnt->mnt_flags & MNT_NODEV)
return -EACCES;
/*FALLTHRU*/
case S_IFIFO:
case S_IFSOCK:
flag &= ~O_TRUNC;
break;
}
error = inode_permission(inode, acc_mode);
if (error)
return error;
/*
* An append-only file must be opened in append mode for writing.
*/
if (IS_APPEND(inode)) {
if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
return -EPERM;
if (flag & O_TRUNC)
return -EPERM;
}
/* O_NOATIME can only be set by the owner or superuser */
if (flag & O_NOATIME && !inode_owner_or_capable(inode))
return -EPERM;
return 0;
}
static int handle_truncate(struct file *filp)
{
struct path *path = &filp->f_path;
struct inode *inode = path->dentry->d_inode;
int error = get_write_access(inode);
if (error)
return error;
/*
* Refuse to truncate files with mandatory locks held on them.
*/
error = locks_verify_locked(inode);
if (!error)
error = security_path_truncate(path);
if (!error) {
error = do_truncate(path->dentry, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
filp);
}
put_write_access(inode);
return error;
}
static inline int open_to_namei_flags(int flag)
{
if ((flag & O_ACCMODE) == 3)
flag--;
return flag;
}
static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
{
int error = security_path_mknod(dir, dentry, mode, 0);
if (error)
return error;
error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
if (error)
return error;
return security_inode_create(dir->dentry->d_inode, dentry, mode);
}
/*
* Attempt to atomically look up, create and open a file from a negative
* dentry.
*
* Returns 0 if successful. The file will have been created and attached to
* @file by the filesystem calling finish_open().
*
* Returns 1 if the file was looked up only or didn't need creating. The
* caller will need to perform the open themselves. @path will have been
* updated to point to the new dentry. This may be negative.
*
* Returns an error code otherwise.
*/
static int atomic_open(struct nameidata *nd, struct dentry *dentry,
struct path *path, struct file *file,
const struct open_flags *op,
bool got_write, bool need_lookup,
int *opened)
{
struct inode *dir = nd->path.dentry->d_inode;
unsigned open_flag = open_to_namei_flags(op->open_flag);
umode_t mode;
int error;
int acc_mode;
int create_error = 0;
struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
BUG_ON(dentry->d_inode);
/* Don't create child dentry for a dead directory. */
if (unlikely(IS_DEADDIR(dir))) {
error = -ENOENT;
goto out;
}
mode = op->mode;
if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
mode &= ~current_umask();
if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) {
open_flag &= ~O_TRUNC;
*opened |= FILE_CREATED;
}
/*
* Checking write permission is tricky, bacuse we don't know if we are
* going to actually need it: O_CREAT opens should work as long as the
* file exists. But checking existence breaks atomicity. The trick is
* to check access and if not granted clear O_CREAT from the flags.
*
* Another problem is returing the "right" error value (e.g. for an
* O_EXCL open we want to return EEXIST not EROFS).
*/
if (((open_flag & (O_CREAT | O_TRUNC)) ||
(open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
if (!(open_flag & O_CREAT)) {
/*
* No O_CREATE -> atomicity not a requirement -> fall
* back to lookup + open
*/
goto no_open;
} else if (open_flag & (O_EXCL | O_TRUNC)) {
/* Fall back and fail with the right error */
create_error = -EROFS;
goto no_open;
} else {
/* No side effects, safe to clear O_CREAT */
create_error = -EROFS;
open_flag &= ~O_CREAT;
}
}
if (open_flag & O_CREAT) {
error = may_o_create(&nd->path, dentry, mode);
if (error) {
create_error = error;
if (open_flag & O_EXCL)
goto no_open;
open_flag &= ~O_CREAT;
}
}
if (nd->flags & LOOKUP_DIRECTORY)
open_flag |= O_DIRECTORY;
file->f_path.dentry = DENTRY_NOT_SET;
file->f_path.mnt = nd->path.mnt;
error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
opened);
if (error < 0) {
if (create_error && error == -ENOENT)
error = create_error;
goto out;
}
acc_mode = op->acc_mode;
if (*opened & FILE_CREATED) {
fsnotify_create(dir, dentry);
acc_mode = MAY_OPEN;
}
if (error) { /* returned 1, that is */
if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
error = -EIO;
goto out;
}
if (file->f_path.dentry) {
dput(dentry);
dentry = file->f_path.dentry;
}
if (create_error && dentry->d_inode == NULL) {
error = create_error;
goto out;
}
goto looked_up;
}
/*
* We didn't have the inode before the open, so check open permission
* here.
*/
error = may_open(&file->f_path, acc_mode, open_flag);
if (error)
fput(file);
out:
dput(dentry);
return error;
no_open:
if (need_lookup) {
dentry = lookup_real(dir, dentry, nd->flags);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (create_error) {
int open_flag = op->open_flag;
error = create_error;
if ((open_flag & O_EXCL)) {
if (!dentry->d_inode)
goto out;
} else if (!dentry->d_inode) {
goto out;
} else if ((open_flag & O_TRUNC) &&
S_ISREG(dentry->d_inode->i_mode)) {
goto out;
}
/* will fail later, go on to get the right error */
}
}
looked_up:
path->dentry = dentry;
path->mnt = nd->path.mnt;
return 1;
}
/*
* Look up and maybe create and open the last component.
*
* Must be called with i_mutex held on parent.
*
* Returns 0 if the file was successfully atomically created (if necessary) and
* opened. In this case the file will be returned attached to @file.
*
* Returns 1 if the file was not completely opened at this time, though lookups
* and creations will have been performed and the dentry returned in @path will
* be positive upon return if O_CREAT was specified. If O_CREAT wasn't
* specified then a negative dentry may be returned.
*
* An error code is returned otherwise.
*
* FILE_CREATE will be set in @*opened if the dentry was created and will be
* cleared otherwise prior to returning.
*/
static int lookup_open(struct nameidata *nd, struct path *path,
struct file *file,
const struct open_flags *op,
bool got_write, int *opened)
{
struct dentry *dir = nd->path.dentry;
struct inode *dir_inode = dir->d_inode;
struct dentry *dentry;
int error;
bool need_lookup;
*opened &= ~FILE_CREATED;
dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
/* Cached positive dentry: will open in f_op->open */
if (!need_lookup && dentry->d_inode)
goto out_no_open;
if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
return atomic_open(nd, dentry, path, file, op, got_write,
need_lookup, opened);
}
if (need_lookup) {
BUG_ON(dentry->d_inode);
dentry = lookup_real(dir_inode, dentry, nd->flags);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
}
/* Negative dentry, just create the file */
if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
umode_t mode = op->mode;
if (!IS_POSIXACL(dir->d_inode))
mode &= ~current_umask();
/*
* This write is needed to ensure that a
* rw->ro transition does not occur between
* the time when the file is created and when
* a permanent write count is taken through
* the 'struct file' in finish_open().
*/
if (!got_write) {
error = -EROFS;
goto out_dput;
}
*opened |= FILE_CREATED;
error = security_path_mknod(&nd->path, dentry, mode, 0);
if (error)
goto out_dput;
error = vfs_create(dir->d_inode, dentry, mode,
nd->flags & LOOKUP_EXCL);
if (error)
goto out_dput;
}
out_no_open:
path->dentry = dentry;
path->mnt = nd->path.mnt;
return 1;
out_dput:
dput(dentry);
return error;
}
/*
* Handle the last step of open()
*/
static int do_last(struct nameidata *nd, struct path *path,
struct file *file, const struct open_flags *op,
int *opened, struct filename *name)
{
struct dentry *dir = nd->path.dentry;
int open_flag = op->open_flag;
bool will_truncate = (open_flag & O_TRUNC) != 0;
bool got_write = false;
int acc_mode = op->acc_mode;
struct inode *inode;
bool symlink_ok = false;
struct path save_parent = { .dentry = NULL, .mnt = NULL };
bool retried = false;
int error;
nd->flags &= ~LOOKUP_PARENT;
nd->flags |= op->intent;
switch (nd->last_type) {
case LAST_DOTDOT:
case LAST_DOT:
error = handle_dots(nd, nd->last_type);
if (error)
return error;
/* fallthrough */
case LAST_ROOT:
error = complete_walk(nd);
if (error)
return error;
audit_inode(name, nd->path.dentry, 0);
if (open_flag & O_CREAT) {
error = -EISDIR;
goto out;
}
goto finish_open;
case LAST_BIND:
error = complete_walk(nd);
if (error)
return error;
audit_inode(name, dir, 0);
goto finish_open;
}
if (!(open_flag & O_CREAT)) {
if (nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
symlink_ok = true;
/* we _can_ be in RCU mode here */
error = lookup_fast(nd, &nd->last, path, &inode);
if (likely(!error))
goto finish_lookup;
if (error < 0)
goto out;
BUG_ON(nd->inode != dir->d_inode);
} else {
/* create side of things */
/*
* This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
* has been cleared when we got to the last component we are
* about to look up
*/
error = complete_walk(nd);
if (error)
return error;
audit_inode(name, dir, 0);
error = -EISDIR;
/* trailing slashes? */
if (nd->last.name[nd->last.len])
goto out;
}
retry_lookup:
if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
error = mnt_want_write(nd->path.mnt);
if (!error)
got_write = true;
/*
* do _not_ fail yet - we might not need that or fail with
* a different error; let lookup_open() decide; we'll be
* dropping this one anyway.
*/
}
mutex_lock(&dir->d_inode->i_mutex);
error = lookup_open(nd, path, file, op, got_write, opened);
mutex_unlock(&dir->d_inode->i_mutex);
if (error <= 0) {
if (error)
goto out;
if ((*opened & FILE_CREATED) ||
!S_ISREG(file->f_path.dentry->d_inode->i_mode))
will_truncate = false;
audit_inode(name, file->f_path.dentry, 0);
goto opened;
}
if (*opened & FILE_CREATED) {
/* Don't check for write permission, don't truncate */
open_flag &= ~O_TRUNC;
will_truncate = false;
acc_mode = MAY_OPEN;
path_to_nameidata(path, nd);
goto finish_open_created;
}
/*
* create/update audit record if it already exists.
*/
if (path->dentry->d_inode)
audit_inode(name, path->dentry, 0);
/*
* If atomic_open() acquired write access it is dropped now due to
* possible mount and symlink following (this might be optimized away if
* necessary...)
*/
if (got_write) {
mnt_drop_write(nd->path.mnt);
got_write = false;
}
error = -EEXIST;
if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
goto exit_dput;
error = follow_managed(path, nd->flags);
if (error < 0)
goto exit_dput;
if (error)
nd->flags |= LOOKUP_JUMPED;
BUG_ON(nd->flags & LOOKUP_RCU);
inode = path->dentry->d_inode;
finish_lookup:
/* we _can_ be in RCU mode here */
error = -ENOENT;
if (!inode) {
path_to_nameidata(path, nd);
goto out;
}
if (should_follow_link(inode, !symlink_ok)) {
if (nd->flags & LOOKUP_RCU) {
if (unlikely(unlazy_walk(nd, path->dentry))) {
error = -ECHILD;
goto out;
}
}
BUG_ON(inode != path->dentry->d_inode);
return 1;
}
if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
path_to_nameidata(path, nd);
} else {
save_parent.dentry = nd->path.dentry;
save_parent.mnt = mntget(path->mnt);
nd->path.dentry = path->dentry;
}
nd->inode = inode;
/* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
error = complete_walk(nd);
if (error) {
path_put(&save_parent);
return error;
}
error = -EISDIR;
if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode))
goto out;
error = -ENOTDIR;
if ((nd->flags & LOOKUP_DIRECTORY) && !nd->inode->i_op->lookup)
goto out;
audit_inode(name, nd->path.dentry, 0);
finish_open:
if (!S_ISREG(nd->inode->i_mode))
will_truncate = false;
if (will_truncate) {
error = mnt_want_write(nd->path.mnt);
if (error)
goto out;
got_write = true;
}
finish_open_created:
error = may_open(&nd->path, acc_mode, open_flag);
if (error)
goto out;
file->f_path.mnt = nd->path.mnt;
error = finish_open(file, nd->path.dentry, NULL, opened);
if (error) {
if (error == -EOPENSTALE)
goto stale_open;
goto out;
}
opened:
error = open_check_o_direct(file);
if (error)
goto exit_fput;
error = ima_file_check(file, op->acc_mode);
if (error)
goto exit_fput;
if (will_truncate) {
error = handle_truncate(file);
if (error)
goto exit_fput;
}
out:
if (got_write)
mnt_drop_write(nd->path.mnt);
path_put(&save_parent);
terminate_walk(nd);
return error;
exit_dput:
path_put_conditional(path, nd);
goto out;
exit_fput:
fput(file);
goto out;
stale_open:
/* If no saved parent or already retried then can't retry */
if (!save_parent.dentry || retried)
goto out;
BUG_ON(save_parent.dentry != dir);
path_put(&nd->path);
nd->path = save_parent;
nd->inode = dir->d_inode;
save_parent.mnt = NULL;
save_parent.dentry = NULL;
if (got_write) {
mnt_drop_write(nd->path.mnt);
got_write = false;
}
retried = true;
goto retry_lookup;
}
static struct file *path_openat(int dfd, struct filename *pathname,
struct nameidata *nd, const struct open_flags *op, int flags)
{
struct file *base = NULL;
struct file *file;
struct path path;
int opened = 0;
int error;
file = get_empty_filp();
if (!file)
return ERR_PTR(-ENFILE);
file->f_flags = op->open_flag;
error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
if (unlikely(error))
goto out;
current->total_link_count = 0;
error = link_path_walk(pathname->name, nd);
if (unlikely(error))
goto out;
error = do_last(nd, &path, file, op, &opened, pathname);
while (unlikely(error > 0)) { /* trailing symlink */
struct path link = path;
void *cookie;
if (!(nd->flags & LOOKUP_FOLLOW)) {
path_put_conditional(&path, nd);
path_put(&nd->path);
error = -ELOOP;
break;
}
error = may_follow_link(&link, nd);
if (unlikely(error))
break;
nd->flags |= LOOKUP_PARENT;
nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
error = follow_link(&link, nd, &cookie);
if (unlikely(error))
break;
error = do_last(nd, &path, file, op, &opened, pathname);
put_link(nd, &link, cookie);
}
out:
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
path_put(&nd->root);
if (base)
fput(base);
if (!(opened & FILE_OPENED)) {
BUG_ON(!error);
put_filp(file);
}
if (unlikely(error)) {
if (error == -EOPENSTALE) {
if (flags & LOOKUP_RCU)
error = -ECHILD;
else
error = -ESTALE;
}
file = ERR_PTR(error);
}
return file;
}
struct file *do_filp_open(int dfd, struct filename *pathname,
const struct open_flags *op, int flags)
{
struct nameidata nd;
struct file *filp;
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
if (unlikely(filp == ERR_PTR(-ECHILD)))
filp = path_openat(dfd, pathname, &nd, op, flags);
if (unlikely(filp == ERR_PTR(-ESTALE)))
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
return filp;
}
struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
const char *name, const struct open_flags *op, int flags)
{
struct nameidata nd;
struct file *file;
struct filename filename = { .name = name };
nd.root.mnt = mnt;
nd.root.dentry = dentry;
flags |= LOOKUP_ROOT;
if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
return ERR_PTR(-ELOOP);
file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
if (unlikely(file == ERR_PTR(-ECHILD)))
file = path_openat(-1, &filename, &nd, op, flags);
if (unlikely(file == ERR_PTR(-ESTALE)))
file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL);
return file;
}
struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path, int is_dir)
{
struct dentry *dentry = ERR_PTR(-EEXIST);
struct nameidata nd;
int err2;
int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd);
if (error)
return ERR_PTR(error);
/*
* Yucky last component or no last component at all?
* (foo/., foo/.., /////)
*/
if (nd.last_type != LAST_NORM)
goto out;
nd.flags &= ~LOOKUP_PARENT;
nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
/* don't fail immediately if it's r/o, at least try to report other errors */
err2 = mnt_want_write(nd.path.mnt);
/*
* Do the final lookup.
*/
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
if (IS_ERR(dentry))
goto unlock;
error = -EEXIST;
if (dentry->d_inode)
goto fail;
/*
* Special case - lookup gave negative, but... we had foo/bar/
* From the vfs_mknod() POV we just have a negative dentry -
* all is fine. Let's be bastards - you had / on the end, you've
* been asking for (non-existent) directory. -ENOENT for you.
*/
if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
error = -ENOENT;
goto fail;
}
if (unlikely(err2)) {
error = err2;
goto fail;
}
*path = nd.path;
return dentry;
fail:
dput(dentry);
dentry = ERR_PTR(error);
unlock:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
if (!err2)
mnt_drop_write(nd.path.mnt);
out:
path_put(&nd.path);
return dentry;
}
EXPORT_SYMBOL(kern_path_create);
void done_path_create(struct path *path, struct dentry *dentry)
{
dput(dentry);
mutex_unlock(&path->dentry->d_inode->i_mutex);
mnt_drop_write(path->mnt);
path_put(path);
}
EXPORT_SYMBOL(done_path_create);
struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, int is_dir)
{
struct filename *tmp = getname(pathname);
struct dentry *res;
if (IS_ERR(tmp))
return ERR_CAST(tmp);
res = kern_path_create(dfd, tmp->name, path, is_dir);
putname(tmp);
return res;
}
EXPORT_SYMBOL(user_path_create);
int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
{
int error = may_create(dir, dentry);
if (error)
return error;
if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
return -EPERM;
if (!dir->i_op->mknod)
return -EPERM;
error = devcgroup_inode_mknod(mode, dev);
if (error)
return error;
error = security_inode_mknod(dir, dentry, mode, dev);
if (error)
return error;
error = dir->i_op->mknod(dir, dentry, mode, dev);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
static int may_mknod(umode_t mode)
{
switch (mode & S_IFMT) {
case S_IFREG:
case S_IFCHR:
case S_IFBLK:
case S_IFIFO:
case S_IFSOCK:
case 0: /* zero mode translates to S_IFREG */
return 0;
case S_IFDIR:
return -EPERM;
default:
return -EINVAL;
}
}
SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
unsigned, dev)
{
struct dentry *dentry;
struct path path;
int error;
error = may_mknod(mode);
if (error)
return error;
dentry = user_path_create(dfd, filename, &path, 0);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (!IS_POSIXACL(path.dentry->d_inode))
mode &= ~current_umask();
error = security_path_mknod(&path, dentry, mode, dev);
if (error)
goto out;
switch (mode & S_IFMT) {
case 0: case S_IFREG:
error = vfs_create(path.dentry->d_inode,dentry,mode,true);
break;
case S_IFCHR: case S_IFBLK:
error = vfs_mknod(path.dentry->d_inode,dentry,mode,
new_decode_dev(dev));
break;
case S_IFIFO: case S_IFSOCK:
error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
break;
}
out:
done_path_create(&path, dentry);
return error;
}
SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
{
return sys_mknodat(AT_FDCWD, filename, mode, dev);
}
int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
int error = may_create(dir, dentry);
unsigned max_links = dir->i_sb->s_max_links;
if (error)
return error;
if (!dir->i_op->mkdir)
return -EPERM;
mode &= (S_IRWXUGO|S_ISVTX);
error = security_inode_mkdir(dir, dentry, mode);
if (error)
return error;
if (max_links && dir->i_nlink >= max_links)
return -EMLINK;
error = dir->i_op->mkdir(dir, dentry, mode);
if (!error)
fsnotify_mkdir(dir, dentry);
return error;
}
SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
{
struct dentry *dentry;
struct path path;
int error;
dentry = user_path_create(dfd, pathname, &path, 1);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (!IS_POSIXACL(path.dentry->d_inode))
mode &= ~current_umask();
error = security_path_mkdir(&path, dentry, mode);
if (!error)
error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
done_path_create(&path, dentry);
return error;
}
SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
{
return sys_mkdirat(AT_FDCWD, pathname, mode);
}
/*
* The dentry_unhash() helper will try to drop the dentry early: we
* should have a usage count of 1 if we're the only user of this
* dentry, and if that is true (possibly after pruning the dcache),
* then we drop the dentry now.
*
* A low-level filesystem can, if it choses, legally
* do a
*
* if (!d_unhashed(dentry))
* return -EBUSY;
*
* if it cannot handle the case of removing a directory
* that is still in use by something else..
*/
void dentry_unhash(struct dentry *dentry)
{
shrink_dcache_parent(dentry);
spin_lock(&dentry->d_lock);
if (dentry->d_count == 1)
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
int vfs_rmdir(struct inode *dir, struct dentry *dentry)
{
int error = may_delete(dir, dentry, 1);
if (error)
return error;
if (!dir->i_op->rmdir)
return -EPERM;
dget(dentry);
mutex_lock(&dentry->d_inode->i_mutex);
error = -EBUSY;
if (d_mountpoint(dentry))
goto out;
error = security_inode_rmdir(dir, dentry);
if (error)
goto out;
shrink_dcache_parent(dentry);
error = dir->i_op->rmdir(dir, dentry);
if (error)
goto out;
dentry->d_inode->i_flags |= S_DEAD;
dont_mount(dentry);
out:
mutex_unlock(&dentry->d_inode->i_mutex);
dput(dentry);
if (!error)
d_delete(dentry);
return error;
}
static long do_rmdir(int dfd, const char __user *pathname)
{
int error = 0;
struct filename *name;
struct dentry *dentry;
struct nameidata nd;
name = user_path_parent(dfd, pathname, &nd);
if (IS_ERR(name))
return PTR_ERR(name);
switch(nd.last_type) {
case LAST_DOTDOT:
error = -ENOTEMPTY;
goto exit1;
case LAST_DOT:
error = -EINVAL;
goto exit1;
case LAST_ROOT:
error = -EBUSY;
goto exit1;
}
nd.flags &= ~LOOKUP_PARENT;
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit1;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto exit2;
if (!dentry->d_inode) {
error = -ENOENT;
goto exit3;
}
error = security_path_rmdir(&nd.path, dentry);
if (error)
goto exit3;
error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
exit3:
dput(dentry);
exit2:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
mnt_drop_write(nd.path.mnt);
exit1:
path_put(&nd.path);
putname(name);
return error;
}
SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
{
return do_rmdir(AT_FDCWD, pathname);
}
int vfs_unlink(struct inode *dir, struct dentry *dentry)
{
int error = may_delete(dir, dentry, 0);
if (error)
return error;
if (!dir->i_op->unlink)
return -EPERM;
mutex_lock(&dentry->d_inode->i_mutex);
if (d_mountpoint(dentry))
error = -EBUSY;
else {
error = security_inode_unlink(dir, dentry);
if (!error) {
error = dir->i_op->unlink(dir, dentry);
if (!error)
dont_mount(dentry);
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
/* We don't d_delete() NFS sillyrenamed files--they still exist. */
if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
fsnotify_link_count(dentry->d_inode);
d_delete(dentry);
}
return error;
}
/*
* Make sure that the actual truncation of the file will occur outside its
* directory's i_mutex. Truncate can take a long time if there is a lot of
* writeout happening, and we don't want to prevent access to the directory
* while waiting on the I/O.
*/
static long do_unlinkat(int dfd, const char __user *pathname)
{
int error;
struct filename *name;
struct dentry *dentry;
struct nameidata nd;
struct inode *inode = NULL;
name = user_path_parent(dfd, pathname, &nd);
if (IS_ERR(name))
return PTR_ERR(name);
error = -EISDIR;
if (nd.last_type != LAST_NORM)
goto exit1;
nd.flags &= ~LOOKUP_PARENT;
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit1;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
/* Why not before? Because we want correct error value */
if (nd.last.name[nd.last.len])
goto slashes;
inode = dentry->d_inode;
if (!inode)
goto slashes;
ihold(inode);
error = security_path_unlink(&nd.path, dentry);
if (error)
goto exit2;
error = vfs_unlink(nd.path.dentry->d_inode, dentry);
exit2:
dput(dentry);
}
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
if (inode)
iput(inode); /* truncate the inode here */
mnt_drop_write(nd.path.mnt);
exit1:
path_put(&nd.path);
putname(name);
return error;
slashes:
error = !dentry->d_inode ? -ENOENT :
S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
goto exit2;
}
SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
{
if ((flag & ~AT_REMOVEDIR) != 0)
return -EINVAL;
if (flag & AT_REMOVEDIR)
return do_rmdir(dfd, pathname);
return do_unlinkat(dfd, pathname);
}
SYSCALL_DEFINE1(unlink, const char __user *, pathname)
{
return do_unlinkat(AT_FDCWD, pathname);
}
int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
{
int error = may_create(dir, dentry);
if (error)
return error;
if (!dir->i_op->symlink)
return -EPERM;
error = security_inode_symlink(dir, dentry, oldname);
if (error)
return error;
error = dir->i_op->symlink(dir, dentry, oldname);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
int, newdfd, const char __user *, newname)
{
int error;
struct filename *from;
struct dentry *dentry;
struct path path;
from = getname(oldname);
if (IS_ERR(from))
return PTR_ERR(from);
dentry = user_path_create(newdfd, newname, &path, 0);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto out_putname;
error = security_path_symlink(&path, dentry, from->name);
if (!error)
error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
done_path_create(&path, dentry);
out_putname:
putname(from);
return error;
}
SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
{
return sys_symlinkat(oldname, AT_FDCWD, newname);
}
int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
{
struct inode *inode = old_dentry->d_inode;
unsigned max_links = dir->i_sb->s_max_links;
int error;
if (!inode)
return -ENOENT;
error = may_create(dir, new_dentry);
if (error)
return error;
if (dir->i_sb != inode->i_sb)
return -EXDEV;
/*
* A link to an append-only or immutable file cannot be created.
*/
if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
return -EPERM;
if (!dir->i_op->link)
return -EPERM;
if (S_ISDIR(inode->i_mode))
return -EPERM;
error = security_inode_link(old_dentry, dir, new_dentry);
if (error)
return error;
mutex_lock(&inode->i_mutex);
/* Make sure we don't allow creating hardlink to an unlinked file */
if (inode->i_nlink == 0)
error = -ENOENT;
else if (max_links && inode->i_nlink >= max_links)
error = -EMLINK;
else
error = dir->i_op->link(old_dentry, dir, new_dentry);
mutex_unlock(&inode->i_mutex);
if (!error)
fsnotify_link(dir, inode, new_dentry);
return error;
}
/*
* Hardlinks are often used in delicate situations. We avoid
* security-related surprises by not following symlinks on the
* newname. --KAB
*
* We don't follow them on the oldname either to be compatible
* with linux 2.0, and to avoid hard-linking to directories
* and other special files. --ADM
*/
SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname, int, flags)
{
struct dentry *new_dentry;
struct path old_path, new_path;
int how = 0;
int error;
if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
return -EINVAL;
/*
* To use null names we require CAP_DAC_READ_SEARCH
* This ensures that not everyone will be able to create
* handlink using the passed filedescriptor.
*/
if (flags & AT_EMPTY_PATH) {
if (!capable(CAP_DAC_READ_SEARCH))
return -ENOENT;
how = LOOKUP_EMPTY;
}
if (flags & AT_SYMLINK_FOLLOW)
how |= LOOKUP_FOLLOW;
error = user_path_at(olddfd, oldname, how, &old_path);
if (error)
return error;
new_dentry = user_path_create(newdfd, newname, &new_path, 0);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
goto out;
error = -EXDEV;
if (old_path.mnt != new_path.mnt)
goto out_dput;
error = may_linkat(&old_path);
if (unlikely(error))
goto out_dput;
error = security_path_link(old_path.dentry, &new_path, new_dentry);
if (error)
goto out_dput;
error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
out_dput:
done_path_create(&new_path, new_dentry);
out:
path_put(&old_path);
return error;
}
SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
{
return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
}
/*
* The worst of all namespace operations - renaming directory. "Perverted"
* doesn't even start to describe it. Somebody in UCB had a heck of a trip...
* Problems:
* a) we can get into loop creation. Check is done in is_subdir().
* b) race potential - two innocent renames can create a loop together.
* That's where 4.4 screws up. Current fix: serialization on
* sb->s_vfs_rename_mutex. We might be more accurate, but that's another
* story.
* c) we have to lock _three_ objects - parents and victim (if it exists).
* And that - after we got ->i_mutex on parents (until then we don't know
* whether the target exists). Solution: try to be smart with locking
* order for inodes. We rely on the fact that tree topology may change
* only under ->s_vfs_rename_mutex _and_ that parent of the object we
* move will be locked. Thus we can rank directories by the tree
* (ancestors first) and rank all non-directories after them.
* That works since everybody except rename does "lock parent, lookup,
* lock child" and rename is under ->s_vfs_rename_mutex.
* HOWEVER, it relies on the assumption that any object with ->lookup()
* has no more than 1 dentry. If "hybrid" objects will ever appear,
* we'd better make sure that there's no link(2) for them.
* d) conversion from fhandle to dentry may come in the wrong moment - when
* we are removing the target. Solution: we will have to grab ->i_mutex
* in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
* ->i_mutex on parents, which works but leads to some truly excessive
* locking].
*/
static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
int error = 0;
struct inode *target = new_dentry->d_inode;
unsigned max_links = new_dir->i_sb->s_max_links;
/*
* If we are going to change the parent - check write permissions,
* we'll need to flip '..'.
*/
if (new_dir != old_dir) {
error = inode_permission(old_dentry->d_inode, MAY_WRITE);
if (error)
return error;
}
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
return error;
dget(new_dentry);
if (target)
mutex_lock(&target->i_mutex);
error = -EBUSY;
if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
goto out;
error = -EMLINK;
if (max_links && !target && new_dir != old_dir &&
new_dir->i_nlink >= max_links)
goto out;
if (target)
shrink_dcache_parent(new_dentry);
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
goto out;
if (target) {
target->i_flags |= S_DEAD;
dont_mount(new_dentry);
}
out:
if (target)
mutex_unlock(&target->i_mutex);
dput(new_dentry);
if (!error)
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
d_move(old_dentry,new_dentry);
return error;
}
static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
struct inode *target = new_dentry->d_inode;
int error;
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
return error;
dget(new_dentry);
if (target)
mutex_lock(&target->i_mutex);
error = -EBUSY;
if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
goto out;
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
goto out;
if (target)
dont_mount(new_dentry);
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
d_move(old_dentry, new_dentry);
out:
if (target)
mutex_unlock(&target->i_mutex);
dput(new_dentry);
return error;
}
int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
int error;
int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
const unsigned char *old_name;
if (old_dentry->d_inode == new_dentry->d_inode)
return 0;
error = may_delete(old_dir, old_dentry, is_dir);
if (error)
return error;
if (!new_dentry->d_inode)
error = may_create(new_dir, new_dentry);
else
error = may_delete(new_dir, new_dentry, is_dir);
if (error)
return error;
if (!old_dir->i_op->rename)
return -EPERM;
old_name = fsnotify_oldname_init(old_dentry->d_name.name);
if (is_dir)
error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
else
error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
if (!error)
fsnotify_move(old_dir, new_dir, old_name, is_dir,
new_dentry->d_inode, old_dentry);
fsnotify_oldname_free(old_name);
return error;
}
SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname)
{
struct dentry *old_dir, *new_dir;
struct dentry *old_dentry, *new_dentry;
struct dentry *trap;
struct nameidata oldnd, newnd;
struct filename *from;
struct filename *to;
int error;
from = user_path_parent(olddfd, oldname, &oldnd);
if (IS_ERR(from)) {
error = PTR_ERR(from);
goto exit;
}
to = user_path_parent(newdfd, newname, &newnd);
if (IS_ERR(to)) {
error = PTR_ERR(to);
goto exit1;
}
error = -EXDEV;
if (oldnd.path.mnt != newnd.path.mnt)
goto exit2;
old_dir = oldnd.path.dentry;
error = -EBUSY;
if (oldnd.last_type != LAST_NORM)
goto exit2;
new_dir = newnd.path.dentry;
if (newnd.last_type != LAST_NORM)
goto exit2;
error = mnt_want_write(oldnd.path.mnt);
if (error)
goto exit2;
oldnd.flags &= ~LOOKUP_PARENT;
newnd.flags &= ~LOOKUP_PARENT;
newnd.flags |= LOOKUP_RENAME_TARGET;
trap = lock_rename(new_dir, old_dir);
old_dentry = lookup_hash(&oldnd);
error = PTR_ERR(old_dentry);
if (IS_ERR(old_dentry))
goto exit3;
/* source must exist */
error = -ENOENT;
if (!old_dentry->d_inode)
goto exit4;
/* unless the source is a directory trailing slashes give -ENOTDIR */
if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
error = -ENOTDIR;
if (oldnd.last.name[oldnd.last.len])
goto exit4;
if (newnd.last.name[newnd.last.len])
goto exit4;
}
/* source should not be ancestor of target */
error = -EINVAL;
if (old_dentry == trap)
goto exit4;
new_dentry = lookup_hash(&newnd);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
goto exit4;
/* target should not be an ancestor of source */
error = -ENOTEMPTY;
if (new_dentry == trap)
goto exit5;
error = security_path_rename(&oldnd.path, old_dentry,
&newnd.path, new_dentry);
if (error)
goto exit5;
error = vfs_rename(old_dir->d_inode, old_dentry,
new_dir->d_inode, new_dentry);
exit5:
dput(new_dentry);
exit4:
dput(old_dentry);
exit3:
unlock_rename(new_dir, old_dir);
mnt_drop_write(oldnd.path.mnt);
exit2:
path_put(&newnd.path);
putname(to);
exit1:
path_put(&oldnd.path);
putname(from);
exit:
return error;
}
SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
{
return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
}
int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
{
int len;
len = PTR_ERR(link);
if (IS_ERR(link))
goto out;
len = strlen(link);
if (len > (unsigned) buflen)
len = buflen;
if (copy_to_user(buffer, link, len))
len = -EFAULT;
out:
return len;
}
/*
* A helper for ->readlink(). This should be used *ONLY* for symlinks that
* have ->follow_link() touching nd only in nd_set_link(). Using (or not
* using) it for any given inode is up to filesystem.
*/
int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct nameidata nd;
void *cookie;
int res;
nd.depth = 0;
cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
if (IS_ERR(cookie))
return PTR_ERR(cookie);
res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
if (dentry->d_inode->i_op->put_link)
dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
return res;
}
int vfs_follow_link(struct nameidata *nd, const char *link)
{
return __vfs_follow_link(nd, link);
}
/* get the link contents into pagecache */
static char *page_getlink(struct dentry * dentry, struct page **ppage)
{
char *kaddr;
struct page *page;
struct address_space *mapping = dentry->d_inode->i_mapping;
page = read_mapping_page(mapping, 0, NULL);
if (IS_ERR(page))
return (char*)page;
*ppage = page;
kaddr = kmap(page);
nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
return kaddr;
}
int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct page *page = NULL;
char *s = page_getlink(dentry, &page);
int res = vfs_readlink(dentry,buffer,buflen,s);
if (page) {
kunmap(page);
page_cache_release(page);
}
return res;
}
void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
{
struct page *page = NULL;
nd_set_link(nd, page_getlink(dentry, &page));
return page;
}
void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
struct page *page = cookie;
if (page) {
kunmap(page);
page_cache_release(page);
}
}
/*
* The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
*/
int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
{
struct address_space *mapping = inode->i_mapping;
struct page *page;
void *fsdata;
int err;
char *kaddr;
unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
if (nofs)
flags |= AOP_FLAG_NOFS;
retry:
err = pagecache_write_begin(NULL, mapping, 0, len-1,
flags, &page, &fsdata);
if (err)
goto fail;
kaddr = kmap_atomic(page);
memcpy(kaddr, symname, len-1);
kunmap_atomic(kaddr);
err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
page, fsdata);
if (err < 0)
goto fail;
if (err < len-1)
goto retry;
mark_inode_dirty(inode);
return 0;
fail:
return err;
}
int page_symlink(struct inode *inode, const char *symname, int len)
{
return __page_symlink(inode, symname, len,
!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
}
const struct inode_operations page_symlink_inode_operations = {
.readlink = generic_readlink,
.follow_link = page_follow_link_light,
.put_link = page_put_link,
};
EXPORT_SYMBOL(user_path_at);
EXPORT_SYMBOL(follow_down_one);
EXPORT_SYMBOL(follow_down);
EXPORT_SYMBOL(follow_up);
EXPORT_SYMBOL(get_write_access); /* nfsd */
EXPORT_SYMBOL(lock_rename);
EXPORT_SYMBOL(lookup_one_len);
EXPORT_SYMBOL(page_follow_link_light);
EXPORT_SYMBOL(page_put_link);
EXPORT_SYMBOL(page_readlink);
EXPORT_SYMBOL(__page_symlink);
EXPORT_SYMBOL(page_symlink);
EXPORT_SYMBOL(page_symlink_inode_operations);
EXPORT_SYMBOL(kern_path);
EXPORT_SYMBOL(vfs_path_lookup);
EXPORT_SYMBOL(inode_permission);
EXPORT_SYMBOL(unlock_rename);
EXPORT_SYMBOL(vfs_create);
EXPORT_SYMBOL(vfs_follow_link);
EXPORT_SYMBOL(vfs_link);
EXPORT_SYMBOL(vfs_mkdir);
EXPORT_SYMBOL(vfs_mknod);
EXPORT_SYMBOL(generic_permission);
EXPORT_SYMBOL(vfs_readlink);
EXPORT_SYMBOL(vfs_rename);
EXPORT_SYMBOL(vfs_rmdir);
EXPORT_SYMBOL(vfs_symlink);
EXPORT_SYMBOL(vfs_unlink);
EXPORT_SYMBOL(dentry_unhash);
EXPORT_SYMBOL(generic_readlink);
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