netdev - Re: [PATCH net] ipv4: remove warning in ip_recv

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Date:   Thu, 24 May 2018 23:59:51 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Network Development <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net] ipv4: remove warning in ip_recv_error

On Thu, May 24, 2018 at 10:18 PM, David Miller <davem@...emloft.net> wrote:
> From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> Date: Wed, 23 May 2018 14:29:52 -0400
>
>> From: Willem de Bruijn <willemb@...gle.com>
>>
>> A precondition check in ip_recv_error triggered on an otherwise benign
>> race. Remove the warning.
>>
>> The warning triggers when passing an ipv6 socket to this ipv4 error
>> handling function. RaceFuzzer was able to trigger it due to a race
>> in setsockopt IPV6_ADDRFORM.
>  ...
>> This socket option converts a v6 socket that is connected to a v4 peer
>> to an v4 socket. It updates the socket on the fly, changing fields in
>> sk as well as other structs. This is inherently non-atomic. It races
>> with the lockless udp_recvmsg path.
>>
>> No other code makes an assumption that these fields are updated
>> atomically. It is benign here, too, as ip_recv_error cares only about
>> the protocol of the skbs enqueued on the error queue, for which
>> sk_family is not a precise predictor (thanks to another isue with
>> IPV6_ADDRFORM).
>>
>> Link: http://lkml.kernel.org/r/20180518120826.GA19515@dragonet.kaist.ac.kr
>> Fixes: ("7ce875e5ecb8 ipv4: warn once on passing AF_INET6 socket to ip_recv_error")
>> Reported-by: DaeRyong Jeong <threeearcat@...il.com>
>> Suggested-by: Eric Dumazet <edumazet@...gle.com>
>> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
>
> Applied and queued up for -stable.
>
> The SHA1_ID doesn't go inside the (" ") of the Fixes tag, I fixed
> it up this time.

Thanks David. Sorry about that.

I'll send a checkpatch.pl patch to catch such typos myself
in the future. Something like

+# Check format of Fixes line
+               if ($in_commit_log && $line =~ /^\s*fixes:/i) {
+                       if ($line !~ /^fixes:\s[0-9a-f]{12,40}\s\(".*"\)$/i) {
+                               WARN("BAD_FIXES",
+                                    "Fixes tag is not of form
\"Fixes: <12+ chars of sha1> \(\"title line\"\)");
+                       }
+               }
+

though it seems that Fixes lines are expressly omitted from strict
commit style checking at the moment. I don't immediately see why.