linux-kernel - Re: [PATCH] [RFC] udp: ipv4: fix potential deadlock on sk_dst

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Message-ID: <alpine.LNX.2.00.1312162343520.12882@pobox.suse.cz>
Date:	Mon, 16 Dec 2013 23:45:20 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Eric Dumazet <edumazet@...gle.com>,
	Shawn Bohrer <sbohrer@...advisors.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [RFC] udp: ipv4: fix potential deadlock on sk_dst_lock

On Mon, 16 Dec 2013, Eric Dumazet wrote:

> > Commit 975022310 ("udp: ipv4: must add synchronization in 
> > udp_sk_rx_dst_set()) caused sk_dst_lock to be obtained in udp4 receive 
> > path, which is happening in softirq context.
> > 
> > inet_bind() is taking sk_dst_lock (through sk_dst_reset()) without turning 
> > IRQs off, which results in the lockdep splat below.
> > 
> > Fix that by disabling IRQs while taking the lock in sk_dst_reset().
> 
> Thanks but I posted this fix instead :
> 
>  http://patchwork.ozlabs.org/patch/301382/

Right, I missed the incarnation in sk_dst_set(), so my patch is apparently 
incomplete anyway.

But using xchg also fixes the issue.

Thanks,

-- 
Jiri Kosina
SUSE Labs
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