Re: [PATCH AUTOSEL for 4.14 015/161] printk: Add console owner and waiter logic to load balance console writes

From: Sasha Levin
Date: Tue Apr 17 2018 - 10:36:56 EST

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:
>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.

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

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