netdev - Re: [PATCH] [net/ipv6] ip6_output: Add ipv6

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Date:   Tue, 28 Jul 2020 07:41:36 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        Gaurav Singh <gaurav1086@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "open list:NETWORKING [IPv4/IPv6]" <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [net/ipv6] ip6_output: Add ipv6_pinfo null check



On 7/27/20 8:12 PM, Cong Wang wrote:
> On Mon, Jul 27, 2020 at 7:14 PM Gaurav Singh <gaurav1086@...il.com> wrote:
>>
>> Add return to fix build issue. Haven't reproduced this issue at
>> my end.
>>
>> My hypothesis is this: In function: ip6_xmit(), we have
>> const struct ipv6_pinfo *np = inet6_sk(sk); which returns NULL.
>>
>> Further down the function, there's a check:
>> if (np) hlimit = hp->htop_limit
> 
> This check exists before git history, at that time 'sk' could be NULL,
> hence 'np', so it does not mean it is still necessary now.
> 
> I looked at all callers of ip6_xmit(), I don't see how it is called with
> a non-full socket, neither 'sk' could be NULL after
> commit b30bd282cbf5c46247a279a2e8d2aae027d9f1bf
> ("[IPV6]: ip6_xmit: remove unnecessary NULL ptr check").
> 
> Thanks.
> 


Agreed.

And again, fact that this patch lacks a Fixes:  tag speaks for itself.

This means the author expects all reviewers to make a deep analysis.

Please bear with us, and add a Fixes: tag so that we can fully understand what was
the bug origin and why a fix is valid.