netdev - Re: Linux 3.1-rc9

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Date:	Tue, 25 Oct 2011 14:30:50 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Miller <davem@...emloft.net>
cc:	torvalds@...ux-foundation.org, sim@...tway.ca,
	netdev@...r.kernel.org, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org, davej@...hat.com,
	schwidefsky@...ibm.com, mingo@...e.hu
Subject: Re: Linux 3.1-rc9

On Tue, 25 Oct 2011, David Miller wrote:

> From: Linus Torvalds <torvalds@...ux-foundation.org>
> Date: Tue, 25 Oct 2011 09:13:48 +0200
> 
> > Added netdev, because this seems to be a generic networking bug (ABBA
> > between sk_lock and icsk_retransmit_timer if my quick scan looks
> > correct).
> > 
> > Davem?
> 
> I suspect that's all just a side effect of whatever is creating the
> preempt_count imbalance.

Something is holding socket lock and it was acquired in sk_clone()
which does bh_lock_sock() and returns with the lock held, though I got
completely lost in the gazillions of possible callchains ...

While staring at it I found an missing unlock in sk_clone() itself,
but that's not the one which causes the leak. Lockdep would have
complained about that separately :)

Thanks,

	tglx

--------->
Subject: net: Unlock sock before calling sk_free()

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Index: linux-2.6/net/core/sock.c
===================================================================
--- linux-2.6.orig/net/core/sock.c
+++ linux-2.6/net/core/sock.c
@@ -1260,6 +1260,7 @@ struct sock *sk_clone(const struct sock 
 			/* It is still raw copy of parent, so invalidate
 			 * destructor and make plain sk_free() */
 			newsk->sk_destruct = NULL;
+			bh_unlock_sock(newsk);
 			sk_free(newsk);
 			newsk = NULL;
 			goto out;

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