[PATCH] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie

[Bharath Vedartham]

v9fs_cache_session_get_cookie assigns a random cachetag to
v9ses->cachetag, if the cachetag is not assigned previously.

v9fs_random_cachetag allocates memory to v9ses->cachetag with kmalloc
and uses scnprintf to fill it up with a cachetag.

But if scnprintf fails, v9ses->cachetag is not freed in the current code causing a memory leak.

Fix this by freeing v9ses->cachetag it v9fs_random_cachetag fails.

This was reported by syzbot, the link to the report is below:
https://syzkaller.appspot.com/bug?id=f012bdf297a7a4c860c38a88b44fbee43fd9bbf3

Reported-by: syzbot+3a030a73b6c1e9833815@xxxxxxxxxxxxxxxxxxxxxxxxx 
Signed-off-by: Bharath Vedartham <linux.bhar@xxxxxxxxx>
---
 fs/9p/cache.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/9p/cache.c b/fs/9p/cache.c
index 9eb3470..4463b91 100644
--- a/fs/9p/cache.c
+++ b/fs/9p/cache.c
@@ -66,6 +66,7 @@ void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses)
 	if (!v9ses->cachetag) {
 		if (v9fs_random_cachetag(v9ses) < 0) {
 			v9ses->fscache = NULL;
+			kfree(v9ses->cachetag);
 			return;
 		}
 	}
-- 
2.7.4