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fuse: convert fuse_file.count from atomic_t to refcount_t

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refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Elena Reshetova 2017-03-03 11:04:03 +02:00 committed by Miklos Szeredi
parent c1ae3cfa0e
commit 4e8c2eb543
2 changed files with 6 additions and 5 deletions
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8
fs/fuse/file.c
View File

@ -58,7 +58,7 @@ struct fuse_file *fuse_file_alloc(struct fuse_conn *fc)
}
INIT_LIST_HEAD(&ff->write_entry);
atomic_set(&ff->count, 1);
refcount_set(&ff->count, 1);
RB_CLEAR_NODE(&ff->polled_node);
init_waitqueue_head(&ff->poll_wait);
@ -77,7 +77,7 @@ void fuse_file_free(struct fuse_file *ff)
static struct fuse_file *fuse_file_get(struct fuse_file *ff)
{
atomic_inc(&ff->count);
refcount_inc(&ff->count);
return ff;
}
@ -88,7 +88,7 @@ static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
static void fuse_file_put(struct fuse_file *ff, bool sync)
{
if (atomic_dec_and_test(&ff->count)) {
if (refcount_dec_and_test(&ff->count)) {
struct fuse_req *req = ff->reserved_req;
if (ff->fc->no_open) {
@ -293,7 +293,7 @@ static int fuse_release(struct inode *inode, struct file *file)
void fuse_sync_release(struct fuse_file *ff, int flags)
{
WARN_ON(atomic_read(&ff->count) != 1);
WARN_ON(refcount_read(&ff->count) > 1);
fuse_prepare_release(ff, flags, FUSE_RELEASE);
/*
* iput(NULL) is a no-op and since the refcount is 1 and everything's

3
fs/fuse/fuse_i.h
View File

@ -24,6 +24,7 @@
#include <linux/workqueue.h>
#include <linux/kref.h>
#include <linux/xattr.h>
#include <linux/refcount.h>
/** Max number of pages that can be used in a single read request */
#define FUSE_MAX_PAGES_PER_REQ 32
@ -137,7 +138,7 @@ struct fuse_file {
u64 nodeid;
/** Refcount */
atomic_t count;
refcount_t count;
/** FOPEN_* flags returned by open */
u32 open_flags;