Re: [PATCH net] af_unix: fix struct pid memory leak

[Willy Tarreau <w@1wt.eu>]

Hi Eric,

On Sun, Jan 24, 2016 at 01:53:50PM -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> Dmitry reported a struct pid leak detected by a syzkaller program.
> 
> Bug happens in unix_stream_recvmsg() when we break the loop when a
> signal is pending, without properly releasing scm.
> 
> Fixes: b3ca9b02b007 ("net: fix multithreaded signal handling in unix recv routines")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Rainer Weikusat <rweikusat@mobileactivedefense.com>
> ---
>  net/unix/af_unix.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index c5bf5ef2bf89..49d5093eb055 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2339,6 +2339,7 @@ again:
>  
>  			if (signal_pending(current)) {
>  				err = sock_intr_errno(timeo);
> +				scm_destroy(&scm);
>  				goto out;
>  			}

Good job on this one! FWIW, I managed to test it on 3.14 and I confirm it
completely fixes the leak there as well. I had to modify it a little bit
however since there's no scm local variable there :

-				scm_destroy(&scm);
+				scm_destroy(siocb->scm);

Cheers,
Willy