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From: Arnd Bergmann <arnd@arndb.de>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, David Miller <davem@davemloft.net>,
	torvalds@linux-foundation.org, akpm@linux-foundation.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [held lock freed] Re: [GIT] Networking
Date: Mon, 21 Mar 2011 16:22:40 +0100
Message-ID: <201103211622.40851.arnd@arndb.de> (raw)
In-Reply-To: <1300719332.2884.370.camel@edumazet-laptop>

On Monday 21 March 2011, Eric Dumazet wrote:
> > diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
> > index 4680b1e..b2cf1db 100644
> > --- a/net/x25/af_x25.c
> > +++ b/net/x25/af_x25.c
> > @@ -669,8 +669,8 @@ static int x25_release(struct socket *sock)
> >  
> >       sock_orphan(sk);
> >  out:
> > -     release_sock(sk);
> >       sock_put(sk);
> > +     release_sock(sk);
> >       return 0;
> >  }
> >  
> 
> Hmm, x25_release() looks fine, I believe no fix is needed.
> 

D'oh. You're right of course. My patch would introduce the bug,
not fix it. Updated patch below.

	Arnd
8<-------------------------
net/appletalk: fix atalk_release use after free

The BKL removal in appletalk introduced a use-after-free problem,
where atalk_destroy_socket frees a sock, but we still release
the socket lock on it.

An easy fix is to take an extra reference on the sock and sock_put
it when returning from atalk_release.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

index 3d4f4b0..206e771 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -1051,6 +1051,7 @@ static int atalk_release(struct socket *sock)
 {
 	struct sock *sk = sock->sk;
 
+	sock_hold(sk);
 	lock_sock(sk);
 	if (sk) {
 		sock_orphan(sk);
@@ -1058,6 +1059,8 @@ static int atalk_release(struct socket *sock)
 		atalk_destroy_socket(sk);
 	}
 	release_sock(sk);
+	sock_put(sk);
+
 	return 0;
 }
 

  reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-03-21  2:51 David Miller
2011-03-21 12:53 ` [held lock freed] " Ingo Molnar
2011-03-21 13:32   ` Eric Dumazet
2011-03-21 14:50     ` Arnd Bergmann
2011-03-21 14:55       ` Eric Dumazet
2011-03-21 15:22         ` Arnd Bergmann [this message]
2011-03-21 16:16           ` Ingo Molnar
2011-03-22  1:18           ` David Miller
2011-03-21 16:15     ` Ingo Molnar
2011-03-21 16:42       ` [slab poison overwritten] " Ingo Molnar
2011-03-21 17:37         ` Ingo Molnar
2011-03-21 17:39         ` Ingo Molnar
2011-03-21 18:07           ` Eric Dumazet
2011-03-21 20:15             ` Eric Dumazet
2011-03-21 22:13               ` Simon Horman
2011-03-21 23:29                 ` Simon Horman
2011-03-22  0:01                   ` Simon Horman
2011-03-22  0:17                     ` Simon Horman
2011-03-22  1:18                       ` Simon Horman
2011-03-22  3:40                         ` David Miller
2011-03-22  3:39                 ` David Miller
2011-03-22  9:56               ` Ingo Molnar
2011-03-22 10:00                 ` Eric Dumazet
2011-03-22 21:52                   ` Simon Horman
2011-03-22  9:07           ` Ingo Molnar
2011-03-22  1:16       ` [held lock freed] " David Miller
2011-03-21 19:24 ` Linus Torvalds
2011-03-21 20:10   ` Eric Dumazet
2011-03-22  4:09   ` David Miller
2011-03-22 10:00   ` Ingo Molnar

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