2019-05-22 19:47:49

by Bharath Vedartham

Subject: [PATCH v2] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie

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: [email protected]
Signed-off-by: Bharath Vedartham <[email protected]>

---
Changes since v2
- Made v9ses->cachetag NULL after freeing to avoid any
side effects.
---
fs/9p/cache.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/9p/cache.c b/fs/9p/cache.c
index 9eb3470..baf72da 100644
--- a/fs/9p/cache.c
+++ b/fs/9p/cache.c
@@ -66,6 +66,8 @@ 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);
+ v9ses->cachetag = NULL;
return;
}
}
--
2.7.4

2019-05-22 19:50:10

by Dominique Martinet

Subject: Re: [PATCH v2] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie

Bharath Vedartham wrote on Thu, May 23, 2019:
> 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: [email protected]
> Signed-off-by: Bharath Vedartham <[email protected]>


Thanks!

I'm on limited internet right now but will run tests and queue this up tomorrow

--
Dominique

2019-05-22 19:52:56

by Bharath Vedartham

Subject: Re: [PATCH v2] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie

Cool! Thanks!

Thank you,
Bharath