netdev - Re: Crash when receiving FIN-ACK in TCP_FIN

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: <0101016eba384308-7dd6b335-8b75-4890-8733-a4dde8064d11-000000@us-west-2.amazonses.com>
Date:   Sat, 30 Nov 2019 02:51:19 +0000
From:   subashab@...eaurora.org
To:     Eric Dumazet <eric.dumazet@...il.com>,
        Josh Hunt <johunt@...mai.com>
Cc:     Neal Cardwell <ncardwell@...gle.com>,
        Netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>
Subject: Re: Crash when receiving FIN-ACK in TCP_FIN_WAIT1 state

>>> Since tcp_write_queue_purge() calls tcp_rtx_queue_purge() and we're 
>>> deleting everything in the retrans queue there, doesn't it make sense 
>>> to zero out all of those associated counters? Obviously clearing 
>>> sacked_out is helping here, but is there a reason to keep track of 
>>> lost_out, retrans_out, etc if retrans queue is now empty? Maybe 
>>> calling tcp_clear_retrans() from tcp_rtx_queue_purge() ?
>> 
>> First, I would like to understand if we hit this problem on current 
>> upstream kernels.
>> 
>> Maybe a backport forgot a dependency.
>> 
>> tcp_write_queue_purge() calls tcp_clear_all_retrans_hints(), not 
>> tcp_clear_retrans(),
>> this is probably for a reason.
>> 
>> Brute force clearing these fields might hide a serious bug.
>> 
> 
> I guess we are all too busy to get more understanding on this :/

Our test devices are on 4.19.x and it is not possible to switch to a 
newer
version. Perhaps Josh has seen this on a newer kernel.