netdev - Re: [PATCH] tcp: dont handle MTU reduction on LISTEN socket

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Message-Id: <20130318.133225.1613717870612687705.davem@davemloft.net>
Date:	Mon, 18 Mar 2013 13:32:25 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, dormando@...ia.net
Subject: Re: [PATCH] tcp: dont handle MTU reduction on LISTEN socket

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 18 Mar 2013 10:01:28 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> When an ICMP ICMP_FRAG_NEEDED (or ICMPV6_PKT_TOOBIG) message finds a
> LISTEN socket, and this socket is currently owned by the user, we
> set TCP_MTU_REDUCED_DEFERRED flag in listener tsq_flags.
> 
> This is bad because if we clone the parent before it had a chance to
> clear the flag, the child inherits the tsq_flags value, and next
> tcp_release_cb() on the child will decrement sk_refcnt.
> 
> Result is that we might free a live TCP socket, as reported by
> Dormando.
> 
> IPv4: Attempt to release TCP socket in state 1
> 
> Fix this issue by testing sk_state against TCP_LISTEN early, so that we
> set TCP_MTU_REDUCED_DEFERRED on appropriate sockets (not a LISTEN one)
> 
> This bug was introduced in commit 563d34d05786
> (tcp: dont drop MTU reduction indications)
> 
> Reported-by: dormando <dormando@...ia.net>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable, thanks.
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