netdev - Re: [PATCH net] packet: unconditionally free po->rollover

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Message-Id: <20190602.181129.1486064709617479611.davem@davemloft.net>
Date:   Sun, 02 Jun 2019 18:11:29 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     willemdebruijn.kernel@...il.com
Cc:     netdev@...r.kernel.org, willemb@...gle.com,
        syzkaller@...glegroups.com, dvyukov@...gle.com
Subject: Re: [PATCH net] packet: unconditionally free po->rollover

From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Date: Fri, 31 May 2019 12:37:23 -0400

> From: Willem de Bruijn <willemb@...gle.com>
> 
> Rollover used to use a complex RCU mechanism for assignment, which had
> a race condition. The below patch fixed the bug and greatly simplified
> the logic.
> 
> The feature depends on fanout, but the state is private to the socket.
> Fanout_release returns f only when the last member leaves and the
> fanout struct is to be freed.
> 
> Destroy rollover unconditionally, regardless of fanout state.
> 
> Fixes: 57f015f5eccf2 ("packet: fix crash in fanout_demux_rollover()")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Diagnosed-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Applied and queued up for -stable.