netdev - Re: [PATCH net] packet: read num_members once in packet_rcv

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Date:	Sun, 21 Jun 2015 09:23:51 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, willemb@...gle.com
Subject: Re: [PATCH net] packet: read num_members once in
 packet_rcv_fanout()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 16 Jun 2015 07:59:11 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> We need to tell compiler it must not read f->num_members multiple
> times. Otherwise testing if num is not zero is flaky, and we could
> attempt an invalid divide by 0 in fanout_demux_cpu()
> 
> Note bug was present in packet_rcv_fanout_hash() and
> packet_rcv_fanout_lb() but final 3.1 had a simple location
> after commit 95ec3eb417115fb ("packet: Add 'cpu' fanout policy.")
> 
> Fixes: dc99f600698dc ("packet: Add fanout support.")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Willem de Bruijn <willemb@...gle.com>
> ---
> Note : I chose to use READ_ONCE() but stable backports should use
> ACCESS_ONCE()

Applied and queued up for -stable, and thanks for the backport notes.
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