netdev - Re: IPv6 TCP seems broken on 32bit x86 (bisected)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <366b2e82-8723-7757-1864-c9fef32dc8f8@gmail.com>
Date: Thu, 24 Aug 2023 12:25:39 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Klara Modin <klarasmodin@...il.com>, netdev@...r.kernel.org
Cc: edumazet@...gle.com, davem@...emloft.net, simon.horman@...igine.com
Subject: Re: IPv6 TCP seems broken on 32bit x86 (bisected)

On 8/24/23 01:00, Klara Modin wrote:
> Hi,
> 
> I recently noticed that IPv6 stopped working properly on my 32 bit x86
> machines with recent kernels. Bisecting leads to
> "fe79bd65c819cc520aa66de65caae8e4cea29c5a net/tcp: refactor
> tcp_inet6_sk()". Reverting this commit on top of
> a5e505a99ca748583dbe558b691be1b26f05d678 fixes the issue.
> 64 bit x86 seems unaffected.

It should be same to what was discussed here

https://lore.kernel.org/netdev/CANn89iLTn6vv9=PvAUccpRNNw6CKcXktixusDpqxqvo+UeLviQ@mail.gmail.com/T/#eb8dca9fc9491cc78fca691e64e601301ec036ce7

Thanks to Eric it should be fixed upstream. Let me check if
it's queued for stable kernels.


> One of the symptoms seems to be that the hop limit is sometimes set to
> zero. Attached is tcpdump output from trying to ssh into the machine
> from a different subnet.
> 
> I also tried http which seems even weirder, the source address is cut
> off or offsetted by 32 bits (results in
> "a5c:1204:84c4:847e:950e:2b3d::", should be
> "2001:678:a5c:1204:84c4:847e:950e:2b3d"). Trying to connect using
> netcat sees the same result as with http.
> 
> Tested on two machines running Gentoo, one with a locally compiled
> kernel and the other compiled from a x86_64 host, both using gcc 13.2.
> If I remember correctly I was using gcc 12.3.1 on the first machine
> when I initially noticed the issue but didn't troubleshoot further at
> the time.
> 
> Please tell me if there's any other information you need.
> 
> Regards,
> Klara Modin

-- 
Pavel Begunkov