linux-kernel - Re: [PATCH] ipv6: fix NULL pointer dereference in ip6

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Message-ID: <d6cacd7d-732c-4fad-576d-a7e9d9ca9537@gmail.com>
Date:   Wed, 8 Dec 2021 08:46:37 -0700
From:   David Ahern <dsahern@...il.com>
To:     Florian Westphal <fw@...len.de>,
        Stephen Suryaputra <ssuryaextr@...il.com>
Cc:     Andrea Mayer <andrea.mayer@...roma2.it>,
        Andrea Righi <andrea.righi@...onical.com>,
        "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Ahmed Abdelsalam <ahabdels@...il.com>,
        Paolo Lungaroni <paolo.lungaroni@...roma2.it>,
        Stefano Salsano <stefano.salsano@...roma2.it>
Subject: Re: [PATCH] ipv6: fix NULL pointer dereference in ip6_output()

On 12/8/21 3:51 AM, Florian Westphal wrote:
> David Ahern <dsahern@...il.com> wrote:
>> On 12/7/21 5:21 PM, Andrea Mayer wrote:
>>> +        IP6CB(skb)->iif = skb->skb_iif;
>>>          [...]
>>>
>>> What do you think?
>>>
>>
>> I like that approach over the need for a fall back in core ipv6 code.
> 
> What if the device is removed after ->iif assignment and before dev lookup?
> 

good point. SR6 should make sure the iif is not cleared, and the
fallback to the skb->dev is still needed in case of delete.