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Commit 4e8c2eb5 authored by Elena Reshetova's avatar Elena Reshetova Committed by Miklos Szeredi
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fuse: convert fuse_file.count from atomic_t to refcount_t 



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: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent c1ae3cfa

fs/fuse/file.c

+4 −4
Original line number Diff line number Diff line
@@ -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

fs/fuse/fuse_i.h

+2 −1
Original line number Diff line number Diff line
@@ -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;