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a8e2b63677
linux/fs/statfs.c
Carlos Maiolino a8e2b63677 Make statfs properly return read-only state after emergency remount 
Emergency remount (sysrq-u) sets MS_RDONLY to the superblock but doesn't set
MNT_READONLY to the mount point.

Once calculate_f_flags() only check for the mount point read only state,
when setting kstatfs flags, after an emergency remount, statfs does not
report the filesystem as read-only, even though it is.

Enable flags_by_sb() to also check for superblock read only state, so the
kstatfs and consequently statfs can properly show the read-only state of
the filesystem.

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-06-29 20:21:06 -04:00

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#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/statfs.h>
#include <linux/security.h>
#include <linux/uaccess.h>
#include <linux/compat.h>
#include "internal.h"
static int flags_by_mnt(int mnt_flags)
{
int flags = 0;
if (mnt_flags & MNT_READONLY)
flags |= ST_RDONLY;
if (mnt_flags & MNT_NOSUID)
flags |= ST_NOSUID;
if (mnt_flags & MNT_NODEV)
flags |= ST_NODEV;
if (mnt_flags & MNT_NOEXEC)
flags |= ST_NOEXEC;
if (mnt_flags & MNT_NOATIME)
flags |= ST_NOATIME;
if (mnt_flags & MNT_NODIRATIME)
flags |= ST_NODIRATIME;
if (mnt_flags & MNT_RELATIME)
flags |= ST_RELATIME;
return flags;
}
static int flags_by_sb(int s_flags)
{
int flags = 0;
if (s_flags & MS_SYNCHRONOUS)
flags |= ST_SYNCHRONOUS;
if (s_flags & MS_MANDLOCK)
flags |= ST_MANDLOCK;
if (s_flags & MS_RDONLY)
flags |= ST_RDONLY;
return flags;
}
static int calculate_f_flags(struct vfsmount *mnt)
{
return ST_VALID | flags_by_mnt(mnt->mnt_flags) |
flags_by_sb(mnt->mnt_sb->s_flags);
}
static int statfs_by_dentry(struct dentry *dentry, struct kstatfs *buf)
{
int retval;
if (!dentry->d_sb->s_op->statfs)
return -ENOSYS;
memset(buf, 0, sizeof(*buf));
retval = security_sb_statfs(dentry);
if (retval)
return retval;
retval = dentry->d_sb->s_op->statfs(dentry, buf);
if (retval == 0 && buf->f_frsize == 0)
buf->f_frsize = buf->f_bsize;
return retval;
}
int vfs_statfs(const struct path *path, struct kstatfs *buf)
{
int error;
error = statfs_by_dentry(path->dentry, buf);
if (!error)
buf->f_flags = calculate_f_flags(path->mnt);
return error;
}
EXPORT_SYMBOL(vfs_statfs);
int user_statfs(const char __user *pathname, struct kstatfs *st)
{
struct path path;
int error;
unsigned int lookup_flags = LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT;
retry:
error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
if (!error) {
error = vfs_statfs(&path, st);
path_put(&path);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
}
return error;
}
int fd_statfs(int fd, struct kstatfs *st)
{
struct fd f = fdget_raw(fd);
int error = -EBADF;
if (f.file) {
error = vfs_statfs(&f.file->f_path, st);
fdput(f);
}
return error;
}
static int do_statfs_native(struct kstatfs *st, struct statfs __user *p)
{
struct statfs buf;
if (sizeof(buf) == sizeof(*st))
memcpy(&buf, st, sizeof(*st));
else {
if (sizeof buf.f_blocks == 4) {
if ((st->f_blocks | st->f_bfree | st->f_bavail |
st->f_bsize | st->f_frsize) &
0xffffffff00000000ULL)
return -EOVERFLOW;
/*
* f_files and f_ffree may be -1; it's okay to stuff
* that into 32 bits
*/
if (st->f_files != -1 &&
(st->f_files & 0xffffffff00000000ULL))
return -EOVERFLOW;
if (st->f_ffree != -1 &&
(st->f_ffree & 0xffffffff00000000ULL))
return -EOVERFLOW;
}
buf.f_type = st->f_type;
buf.f_bsize = st->f_bsize;
buf.f_blocks = st->f_blocks;
buf.f_bfree = st->f_bfree;
buf.f_bavail = st->f_bavail;
buf.f_files = st->f_files;
buf.f_ffree = st->f_ffree;
buf.f_fsid = st->f_fsid;
buf.f_namelen = st->f_namelen;
buf.f_frsize = st->f_frsize;
buf.f_flags = st->f_flags;
memset(buf.f_spare, 0, sizeof(buf.f_spare));
}
if (copy_to_user(p, &buf, sizeof(buf)))
return -EFAULT;
return 0;
}
static int do_statfs64(struct kstatfs *st, struct statfs64 __user *p)
{
struct statfs64 buf;
if (sizeof(buf) == sizeof(*st))
memcpy(&buf, st, sizeof(*st));
else {
buf.f_type = st->f_type;
buf.f_bsize = st->f_bsize;
buf.f_blocks = st->f_blocks;
buf.f_bfree = st->f_bfree;
buf.f_bavail = st->f_bavail;
buf.f_files = st->f_files;
buf.f_ffree = st->f_ffree;
buf.f_fsid = st->f_fsid;
buf.f_namelen = st->f_namelen;
buf.f_frsize = st->f_frsize;
buf.f_flags = st->f_flags;
memset(buf.f_spare, 0, sizeof(buf.f_spare));
}
if (copy_to_user(p, &buf, sizeof(buf)))
return -EFAULT;
return 0;
}
SYSCALL_DEFINE2(statfs, const char __user *, pathname, struct statfs __user *, buf)
{
struct kstatfs st;
int error = user_statfs(pathname, &st);
if (!error)
error = do_statfs_native(&st, buf);
return error;
}
SYSCALL_DEFINE3(statfs64, const char __user *, pathname, size_t, sz, struct statfs64 __user *, buf)
{
struct kstatfs st;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = user_statfs(pathname, &st);
if (!error)
error = do_statfs64(&st, buf);
return error;
}
SYSCALL_DEFINE2(fstatfs, unsigned int, fd, struct statfs __user *, buf)
{
struct kstatfs st;
int error = fd_statfs(fd, &st);
if (!error)
error = do_statfs_native(&st, buf);
return error;
}
SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, size_t, sz, struct statfs64 __user *, buf)
{
struct kstatfs st;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = fd_statfs(fd, &st);
if (!error)
error = do_statfs64(&st, buf);
return error;
}
int vfs_ustat(dev_t dev, struct kstatfs *sbuf)
{
struct super_block *s = user_get_super(dev);
int err;
if (!s)
return -EINVAL;
err = statfs_by_dentry(s->s_root, sbuf);
drop_super(s);
return err;
}
SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
{
struct ustat tmp;
struct kstatfs sbuf;
int err = vfs_ustat(new_decode_dev(dev), &sbuf);
if (err)
return err;
memset(&tmp,0,sizeof(struct ustat));
tmp.f_tfree = sbuf.f_bfree;
tmp.f_tinode = sbuf.f_ffree;
return copy_to_user(ubuf, &tmp, sizeof(struct ustat)) ? -EFAULT : 0;
}
#ifdef CONFIG_COMPAT
static int put_compat_statfs(struct compat_statfs __user *ubuf, struct kstatfs *kbuf)
{
if (sizeof ubuf->f_blocks == 4) {
if ((kbuf->f_blocks | kbuf->f_bfree | kbuf->f_bavail |
kbuf->f_bsize | kbuf->f_frsize) & 0xffffffff00000000ULL)
return -EOVERFLOW;
/* f_files and f_ffree may be -1; it's okay
* to stuff that into 32 bits */
if (kbuf->f_files != 0xffffffffffffffffULL
&& (kbuf->f_files & 0xffffffff00000000ULL))
return -EOVERFLOW;
if (kbuf->f_ffree != 0xffffffffffffffffULL
&& (kbuf->f_ffree & 0xffffffff00000000ULL))
return -EOVERFLOW;
}
if (!access_ok(VERIFY_WRITE, ubuf, sizeof(*ubuf)) ||
__put_user(kbuf->f_type, &ubuf->f_type) ||
__put_user(kbuf->f_bsize, &ubuf->f_bsize) ||
__put_user(kbuf->f_blocks, &ubuf->f_blocks) ||
__put_user(kbuf->f_bfree, &ubuf->f_bfree) ||
__put_user(kbuf->f_bavail, &ubuf->f_bavail) ||
__put_user(kbuf->f_files, &ubuf->f_files) ||
__put_user(kbuf->f_ffree, &ubuf->f_ffree) ||
__put_user(kbuf->f_namelen, &ubuf->f_namelen) ||
__put_user(kbuf->f_fsid.val[0], &ubuf->f_fsid.val[0]) ||
__put_user(kbuf->f_fsid.val[1], &ubuf->f_fsid.val[1]) ||
__put_user(kbuf->f_frsize, &ubuf->f_frsize) ||
__put_user(kbuf->f_flags, &ubuf->f_flags) ||
__clear_user(ubuf->f_spare, sizeof(ubuf->f_spare)))
return -EFAULT;
return 0;
}
/*
* The following statfs calls are copies of code from fs/statfs.c and
* should be checked against those from time to time
*/
COMPAT_SYSCALL_DEFINE2(statfs, const char __user *, pathname, struct compat_statfs __user *, buf)
{
struct kstatfs tmp;
int error = user_statfs(pathname, &tmp);
if (!error)
error = put_compat_statfs(buf, &tmp);
return error;
}
COMPAT_SYSCALL_DEFINE2(fstatfs, unsigned int, fd, struct compat_statfs __user *, buf)
{
struct kstatfs tmp;
int error = fd_statfs(fd, &tmp);
if (!error)
error = put_compat_statfs(buf, &tmp);
return error;
}
static int put_compat_statfs64(struct compat_statfs64 __user *ubuf, struct kstatfs *kbuf)
{
if (sizeof(ubuf->f_bsize) == 4) {
if ((kbuf->f_type | kbuf->f_bsize | kbuf->f_namelen |
kbuf->f_frsize | kbuf->f_flags) & 0xffffffff00000000ULL)
return -EOVERFLOW;
/* f_files and f_ffree may be -1; it's okay
* to stuff that into 32 bits */
if (kbuf->f_files != 0xffffffffffffffffULL
&& (kbuf->f_files & 0xffffffff00000000ULL))
return -EOVERFLOW;
if (kbuf->f_ffree != 0xffffffffffffffffULL
&& (kbuf->f_ffree & 0xffffffff00000000ULL))
return -EOVERFLOW;
}
if (!access_ok(VERIFY_WRITE, ubuf, sizeof(*ubuf)) ||
__put_user(kbuf->f_type, &ubuf->f_type) ||
__put_user(kbuf->f_bsize, &ubuf->f_bsize) ||
__put_user(kbuf->f_blocks, &ubuf->f_blocks) ||
__put_user(kbuf->f_bfree, &ubuf->f_bfree) ||
__put_user(kbuf->f_bavail, &ubuf->f_bavail) ||
__put_user(kbuf->f_files, &ubuf->f_files) ||
__put_user(kbuf->f_ffree, &ubuf->f_ffree) ||
__put_user(kbuf->f_namelen, &ubuf->f_namelen) ||
__put_user(kbuf->f_fsid.val[0], &ubuf->f_fsid.val[0]) ||
__put_user(kbuf->f_fsid.val[1], &ubuf->f_fsid.val[1]) ||
__put_user(kbuf->f_frsize, &ubuf->f_frsize) ||
__put_user(kbuf->f_flags, &ubuf->f_flags) ||
__clear_user(ubuf->f_spare, sizeof(ubuf->f_spare)))
return -EFAULT;
return 0;
}
COMPAT_SYSCALL_DEFINE3(statfs64, const char __user *, pathname, compat_size_t, sz, struct compat_statfs64 __user *, buf)
{
struct kstatfs tmp;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = user_statfs(pathname, &tmp);
if (!error)
error = put_compat_statfs64(buf, &tmp);
return error;
}
COMPAT_SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, compat_size_t, sz, struct compat_statfs64 __user *, buf)
{
struct kstatfs tmp;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = fd_statfs(fd, &tmp);
if (!error)
error = put_compat_statfs64(buf, &tmp);
return error;
}
/*
* This is a copy of sys_ustat, just dealing with a structure layout.
* Given how simple this syscall is that apporach is more maintainable
* than the various conversion hacks.
*/
COMPAT_SYSCALL_DEFINE2(ustat, unsigned, dev, struct compat_ustat __user *, u)
{
struct compat_ustat tmp;
struct kstatfs sbuf;
int err = vfs_ustat(new_decode_dev(dev), &sbuf);
if (err)
return err;
memset(&tmp, 0, sizeof(struct compat_ustat));
tmp.f_tfree = sbuf.f_bfree;
tmp.f_tinode = sbuf.f_ffree;
if (copy_to_user(u, &tmp, sizeof(struct compat_ustat)))
return -EFAULT;
return 0;
}
#endif
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