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Subject: Re: [PATCH 4.19 000/139] 4.19.7-stable review
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
References: <20181204103649.950154335@linuxfoundation.org>
 <716b46ef-03da-9656-92fd-3823f31f5ce6@linaro.org>
 <20181205065851.GA16346@kroah.com>
From:   Rafael David Tinoco <rafael.tinoco@linaro.org>
Organization: Linaro
Message-ID: <e38e63a3-c898-61e8-2140-73e9f05aec33@linaro.org>
Date:   Wed, 5 Dec 2018 10:08:28 -0200
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On 12/5/18 4:58 AM, Greg Kroah-Hartman wrote:
> On Tue, Dec 04, 2018 at 07:09:46PM -0200, Rafael David Tinoco wrote:
>> On 12/4/18 8:48 AM, Greg Kroah-Hartman wrote:
>>> This is the start of the stable review cycle for the 4.19.7 release.
>>> There are 139 patches in this series, all will be posted as a response
>>> to this one.  If anyone has any issues with these being applied, please
>>> let me know.
>>>
>>> Responses should be made by Thu Dec  6 10:36:22 UTC 2018.
>>> Anything received after that time might be too late.
>>>
>>> The whole patch series can be found in one patch at:
>>> 	https://www.kernel.org/pub/linux/kernel/v4.x/stable-review/patch-4.19.7-rc1.gz
>>> or in the git tree and branch at:
>>> 	git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.19.y
>>> and the diffstat can be found below.
>>>
>>> thanks,
>>>
>>> greg k-h
>>
>> During functional tests for this v4.19 release, we faced a PANIC,
>> described bellow, but unlikely related to this specific v4.19 version.
>>
>> First a WARN() at tcp_output.c:
>>
>> tcp_send_loss_probe():
>> ...
>> 	/* Retransmit last segment. */
>> 	if (WARN_ON(!skb))
>> 		goto rearm_timer;
>> ...
>>
>> [  173.557528] WARNING: CPU: 1 PID: 0 at
>> /srv/oe/build/tmp-rpb-glibc/work-shared/juno/kernel-source/net/ipv4/tcp_output.c:2485
>> tcp_send_loss_probe+0x164/0x1e8
>> [  173.571425] Modules linked in: crc32_ce crct10dif_ce fuse
>> [  173.576804] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.7-rc1 #1
>> [  173.583014] Hardware name: ARM Juno development board (r2) (DT)
> 
> So only this one machine saw this failure?
> 
> If you can reproduce it again, bisection would be great to do if
> possible.

Yes, the only machine... I'm afraid this issue is intermittent and
depends on TCP Tail Loss and a specific race causing the NULL
dereference, so bisection would be tricky since it has happened
independently of the functional test that was running. I have also
copied authors for the Tail Loss code to check if they got any clues
even without KASAN data.

Thank you,
-
Rafael D. Tinoco