netdev - Re: [PATCH net] tcp/dccp: block BH for SYN processing

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Message-Id: <20170301.150443.1062358693675562555.davem@davemloft.net>
Date:   Wed, 01 Mar 2017 15:04:43 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     edumazet@...gle.com, andreyknvl@...gle.com, netdev@...r.kernel.org,
        dvyukov@...gle.com, soheil@...gle.com, ast@...nel.org
Subject: Re: [PATCH net] tcp/dccp: block BH for SYN processing

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 01 Mar 2017 08:39:49 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> SYN processing really was meant to be handled from BH.
> 
> When I got rid of BH blocking while processing socket backlog
> in commit 5413d1babe8f ("net: do not block BH while processing socket
> backlog"), I forgot that a malicious user could transition to TCP_LISTEN
> from a state that allowed (SYN) packets to be parked in the socket
> backlog while socket is owned by the thread doing the listen() call.
> 
> Sure enough syzkaller found this and reported the bug ;)
 ...
> Fixes: 5413d1babe8f ("net: do not block BH while processing socket backlog")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>

Applied and queued up for -stable, thanks.