From: Bharath Vedartham <linux.bhar@gmail.com>
Date: Thu, 23 May 2019 01:15:19 +0530
Subject: 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie
Git-commit: 962a991c5de18452d6c429d99f3039387cf5cbb0
Patch-mainline: 5.4-rc1
References: bnc#1151927 5.3.5

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

Link: http://lkml.kernel.org/r/20190522194519.GA5313@bharath12345-Inspiron-5559
Reported-by: syzbot+3a030a73b6c1e9833815@syzkaller.appspotmail.com
Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/9p/cache.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/9p/cache.c
+++ b/fs/9p/cache.c
@@ -51,6 +51,8 @@ void v9fs_cache_session_get_cookie(struc
 	if (!v9ses->cachetag) {
 		if (v9fs_random_cachetag(v9ses) < 0) {
 			v9ses->fscache = NULL;
+			kfree(v9ses->cachetag);
+			v9ses->cachetag = NULL;
 			return;
 		}
 	}