netdev - Re: [PATCH] ipv4: fix a race in ip4_datagram_release

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Message-Id: <20140611.153954.494439641088532676.davem@davemloft.net>
Date:	Wed, 11 Jun 2014 15:39:54 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	preobr@...gle.com, dormando@...ia.net,
	steffen.klassert@...unet.com, paulmck@...ux.vnet.ibm.com,
	netdev@...r.kernel.org, kcc@...gle.com, dvyukov@...gle.com,
	larsbull@...gle.com, edumazet@...gle.com, brutus@...gle.com,
	maze@...gle.com, alexei.starovoitov@...il.com
Subject: Re: [PATCH] ipv4: fix a race in ip4_datagram_release_cb()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 10 Jun 2014 06:43:01 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Alexey gave a AddressSanitizer[1] report that finally gave a good hint
> at where was the origin of various problems already reported by Dormando
> in the past [2]
> 
> Problem comes from the fact that UDP can have a lockless TX path, and
> concurrent threads can manipulate sk_dst_cache, while another thread,
> is holding socket lock and calls __sk_dst_set() in
> ip4_datagram_release_cb() (this was added in linux-3.8)
> 
> It seems that all we need to do is to use sk_dst_check() and
> sk_dst_set() so that all the writers hold same spinlock
> (sk->sk_dst_lock) to prevent corruptions.
> 
> TCP stack do not need this protection, as all sk_dst_cache writers hold
> the socket lock.
> 
> [1]
> https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerForKernel
 ...
> Reported-by: Alexey Preobrazhensky <preobr@...gle.com>
> Reported-by: dormando <dormando@...ia.ne>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Fixes: 8141ed9fcedb2 ("ipv4: Add a socket release callback for datagram sockets")

Applied and queued up for -stable.
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