netdev - Re: [PATCH v2 net] net/packet: fix a race in packet_bind() and packet

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Date:   Tue, 28 Nov 2017 11:14:43 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org, fruggeri@...stanetworks.com,
        willemb@...gle.com
Subject: Re: [PATCH v2 net] net/packet: fix a race in packet_bind() and
 packet_notifier()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 28 Nov 2017 08:03:30 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> syzbot reported crashes [1] and provided a C repro easing bug hunting.
> 
> When/if packet_do_bind() calls __unregister_prot_hook() and releases
> po->bind_lock, another thread can run packet_notifier() and process an
> NETDEV_UP event.
> 
> This calls register_prot_hook() and hooks again the socket right before
> first thread is able to grab again po->bind_lock.
> 
> Fixes this issue by temporarily setting po->num to 0, as suggested by
> David Miller.
> 
> [1]
 ...
> Fixes: 30f7ea1c2b5f ("packet: race condition in packet_bind")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Cc: Francesco Ruggeri <fruggeri@...stanetworks.com>

Applied and queued up for -stable.