linux-kernel - Re: net/icmp: null-ptr-deref in icmp6

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Message-ID: <65c99b22-9336-ebfe-064b-8a2b3ee3c8dd@cumulusnetworks.com>
Date:   Tue, 22 Nov 2016 22:10:37 -0500
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net/icmp: null-ptr-deref in icmp6_send

On 11/22/16 1:11 PM, Cong Wang wrote:
> I have no idea what commit 5d41ce29e tried to fix, but we already
> use skb->dev a few lines before l3mdev_master_ifindex(), so I don't
> understand why skb->dev could be NULL, maybe just for vrf dev?

skb->dev can be null depending on when icmp6_send / icmpv6_send is called. Clearly I missed the ipv6_parse_hopopts -> icmpv6_param_prob path. I'll send a fix when I get back from PTO.