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

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Message-ID: <20160125010627.GB14576@1wt.eu>
Date:	Mon, 25 Jan 2016 02:06:27 +0100
From:	Willy Tarreau <w@....eu>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	netdev <netdev@...r.kernel.org>,
	Rainer Weikusat <rweikusat@...ileactivedefense.com>,
	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Vladimir Davydov <vdavydov@...tuozzo.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [PATCH net] af_unix: fix struct pid memory leak

Hi Eric,

On Sun, Jan 24, 2016 at 01:53:50PM -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.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@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Rainer Weikusat <rweikusat@...ileactivedefense.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