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* [PATCH] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie
@ 2019-05-22 19:16 Bharath Vedartham
  2019-05-22 19:21 ` Dominique Martinet
  0 siblings, 1 reply; 2+ messages in thread
From: Bharath Vedartham @ 2019-05-22 19:16 UTC (permalink / raw)
  To: ericvh, lucho, asmadeus; +Cc: v9fs-developer, linux-kernel

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@syzkaller.appspotmail.com 
Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com>
---
 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


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie
  2019-05-22 19:16 [PATCH] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie Bharath Vedartham
@ 2019-05-22 19:21 ` Dominique Martinet
  0 siblings, 0 replies; 2+ messages in thread
From: Dominique Martinet @ 2019-05-22 19:21 UTC (permalink / raw)
  To: Bharath Vedartham; +Cc: ericvh, lucho, v9fs-developer, linux-kernel

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: syzbot+3a030a73b6c1e9833815@syzkaller.appspotmail.com 
> Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com>
> ---
>  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);

I would also reset v9ses->cachetag to NULL just in case,
v9fs_cache_session_get_cookie will use v9ses->cachetag as it is if it is
not null and you were leaving an invalid pointer there

I do not see any reason it could be called multiple times but
v9fs_cache_session_get_cookie does not return any error (void function)
so something later on could try to use that cachetag incorrectly later
on

Thanks,
-- 
Dominique

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2019-05-22 20:03 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
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2019-05-22 19:16 [PATCH] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie Bharath Vedartham
2019-05-22 19:21 ` Dominique Martinet

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