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: 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>

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index ec238fb5a584b1c3cc5bc545806575160f78cde4..70770a0db73412c7a27377b02498258b2a5b9220 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -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

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 32ac2c9b09c0302c99337c374263a6fa428b5cf4..1d6d67e64f49add9daa37492e66d0df548b0eaf3 100644 (file)
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -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;