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Subject: Re: Steam is broken on new kernels
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        "Pierre-Loup A. Griffais" <pgriffais@valvesoftware.com>,
        Eric Dumazet <edumazet@google.com>,
        lkml <linux-kernel@vger.kernel.org>
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 <20190626022923.GA14595@kroah.com>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <53b23451-f45b-932d-a2f8-15f74f07a849@roeck-us.net>
Date:   Tue, 25 Jun 2019 20:43:38 -0700
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On 6/25/19 7:29 PM, Greg Kroah-Hartman wrote:
> On Tue, Jun 25, 2019 at 07:02:20PM -0700, Guenter Roeck wrote:
>> Hi Greg,
>>
>> On Sat, Jun 22, 2019 at 09:37:53AM +0200, Greg Kroah-Hartman wrote:
>>> On Fri, Jun 21, 2019 at 10:28:21PM -0700, Linus Torvalds wrote:
>>>> On Fri, Jun 21, 2019 at 6:03 PM Pierre-Loup A. Griffais
>>>> <pgriffais@valvesoftware.com> wrote:
>>>>>
>>>>> I applied Eric's path to the tip of the branch and ran that kernel and
>>>>> the bug didn't occur through several logout / login cycles, so things
>>>>> look good at first glance. I'll keep running that kernel and report back
>>>>> if anything crops up in the future, but I believe we're good, beyond
>>>>> getting distros to ship this additional fix.
>>>>
>>>> Good. It's now in my tree, so we can get it quickly into stable and
>>>> then quickly to distributions.
>>>>
>>>> Greg, it's commit b6653b3629e5 ("tcp: refine memory limit test in
>>>> tcp_fragment()"), and I'm building it right now and I'll push it out
>>>> in a couple of minutes assuming nothing odd is going on.
>>>
>>> This looks good for 4.19 and 5.1, so I'll push out new stable kernels in
>>> a bit for them.
>>>
>>> But for 4.14 and older, we don't have the "hint" to know this is an
>>> outbound going packet and not to apply these checks at that point in
>>> time, so this patch doesn't work.
>>>
>>> I'll see if I can figure anything else later this afternoon for those
>>> kernels...
>>>
>>
>> I may have missed it, but I don't see a fix for the problem in
>> older stable branches. Any news ?
>>
>> One possibility might be be to apply the part of 75c119afe14f7 which
>> introduces TCP_FRAG_IN_WRITE_QUEUE and TCP_FRAG_IN_RTX_QUEUE, if that
>> is acceptable.
> 
> That's what people have already discussed on the stable mailing list a
> few hours ago, hopefully a patch shows up soon as I'm traveling at the
> moment and can't do it myself...
> 

Sounds good. Let me know if nothing shows up; I'll be happy to do it
if needed.

Guenter