netdev - Re: [PATCH net] ipv6: make icmp6_send() robust against null skb->dev

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Date:   Fri, 04 Jan 2019 13:40:56 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        p.sawicki2@...tner.samsung.com, casey@...aufler-ca.com,
        syzkaller@...glegroups.com
Subject: Re: [PATCH net] ipv6: make icmp6_send() robust against null
 skb->dev

From: Eric Dumazet <edumazet@...gle.com>
Date: Fri,  4 Jan 2019 11:00:00 -0800

> syzbot was able to crash one host with the following stack trace :
 ...
> This is because a RX packet found socket owned by user and
> was stored into socket backlog. Before leaving RCU protected section,
> skb->dev was cleared in __sk_receive_skb(). When socket backlog
> was finally handled at release_sock() time, skb was fed to
> smack_socket_sock_rcv_skb() then icmp6_send()
> 
> We could fix the bug in smack_socket_sock_rcv_skb(), or simply
> make icmp6_send() more robust against such possibility.
> 
> In the future we might provide to icmp6_send() the net pointer
> instead of infering it.
> 
> Fixes: d66a8acbda92 ("Smack: Inform peer that IPv6 traffic has been blocked")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Piotr Sawicki <p.sawicki2@...tner.samsung.com>
> Cc: Casey Schaufler <casey@...aufler-ca.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied and queued up for -stable, thanks.