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From: Michal Hocko <mhocko@kernel.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: brookxu <brookxu.cn@gmail.com>,
	hannes@cmpxchg.org, vdavydov.dev@gmail.com,
	akpm@linux-foundation.org, cgroups@vger.kernel.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2] memcg: fix NULL pointer dereference in __mem_cgroup_usage_unregister_event
Date: Tue, 10 Mar 2020 12:17:10 +0100	[thread overview]
Message-ID: <20200310111710.GF8447@dhcp22.suse.cz> (raw)
In-Reply-To: <20200310104149.5c3pc75y6ny5hixb@box>

On Tue 10-03-20 13:41:49, Kirill A. Shutemov wrote:
> On Tue, Mar 10, 2020 at 10:48:36AM +0100, Michal Hocko wrote:
> > [Cc Kirill, I didn't realize he has implemented this code]
> 
> My first non-trivial mm contribution :P

Everybody has to pay for sins of youth :p

[...]

> > It seems that the code has been broken since 2c488db27b61 ("memcg: clean
> > up memory thresholds"). We've had 371528caec55 ("mm: memcg: Correct
> > unregistring of events attached to the same eventfd") but it didn't
> > catch this case for some reason. Unless I am missing something the code
> > was broken back then already. Kirill please double check after me.
> 
> I think the issue exitsted before 2c488db27b61. The fields had different
> names back then.
> 
> The logic to make unregister never-fail is added in 907860ed381a
> ("cgroups: make cftype.unregister_event() void-returning"). I believe the
> Fixes should point there.

Yes, you seem to be right. It doesn't make a difference much as both
went in to the same kernel but a proper Fixes tag is really valuable.

Thanks for looking into that.

-- 
Michal Hocko
SUSE Labs


      reply	other threads:[~2020-03-10 11:17 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-06  1:02 [PATCHv2] memcg: fix NULL pointer dereference in __mem_cgroup_usage_unregister_event brookxu
2020-03-10  9:48 ` Michal Hocko
2020-03-10 10:41   ` Kirill A. Shutemov
2020-03-10 11:17     ` Michal Hocko [this message]

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