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Message-ID: <20180417143641.GV2341@sasha-vm>
Date: Tue, 17 Apr 2018 14:36:44 +0000
From: Sasha Levin <Alexander.Levin@...rosoft.com>
To: Michal Hocko <mhocko@...nel.org>
CC: Petr Mladek <pmladek@...e.com>, Greg KH <greg@...ah.com>,
Pavel Machek <pavel@....cz>,
Steven Rostedt <rostedt@...dmis.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"stable@...r.kernel.org" <stable@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Cong Wang <xiyou.wangcong@...il.com>,
Dave Hansen <dave.hansen@...el.com>,
Johannes Weiner <hannes@...xchg.org>,
Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
Peter Zijlstra <peterz@...radead.org>, Jan Kara <jack@...e.cz>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Byungchul Park <byungchul.park@....com>,
Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH AUTOSEL for 4.14 015/161] printk: Add console owner and
waiter logic to load balance console writes
On Tue, Apr 17, 2018 at 04:22:46PM +0200, Michal Hocko wrote:
>On Tue 17-04-18 13:39:33, Sasha Levin wrote:
>[...]
>> But mm/ commits don't come only from these people. Here's a concrete
>> example we can discuss:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c61611f70958d86f659bca25c02ae69413747a8d
>
>I would be really careful. Because that reqiures to audit all callers to
>be compliant with the change. This is just _too_ easy to backport
>without noticing a failure. Now consider the other side. Is there any
>real bug report backing this? This behavior was like that for quite some
>time but I do not remember any actual bug report and the changelog
>doesn't mention one either. It is about theoretical problem.
https://lkml.org/lkml/2018/3/19/430
There's even a fun little reproducer that allowed me to confirm it's an
issue (at least) on 4.15.
Heck, it might even qualify as a CVE.
>So if this was to be merged to stable then the changelog should contain
>a big fat warning about the existing users and how they should be
>checked.
So what I'm asking is why *wasn't* it sent to stable? Yes, it requires
additional work backporting this, but what I'm saying is that this
didn't happen at all.
>Besides that I can see Reviewed-by: akpm and Andrew is usually very
>careful about stable backports so there probably _was_ a reson to
>exclude stable.
>--
>Michal Hocko
>SUSE Labs
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