From: Andrew Morton <akpm@linux-foundation.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Michal Hocko <mhocko@suse.com>,
mm-commits@vger.kernel.org,
syzbot+2d2aeadc6ce1e1f11d45@syzkaller.appspotmail.com,
shakeelb@google.com, roman.gushchin@linux.dev,
hannes@cmpxchg.org, linux-kernel@vger.kernel.org
Subject: Re: + mm-memcontrol-fix-potential-oom_lock-recursion-deadlock.patch added to mm-unstable branch
Date: Tue, 26 Jul 2022 11:50:29 -0700 [thread overview]
Message-ID: <20220726115029.ead4b2dfcd8b3df8e31ccc00@linux-foundation.org> (raw)
In-Reply-To: <ac3a7af1-08c6-e2de-b93c-327ce6839830@I-love.SAKURA.ne.jp>
On Tue, 26 Jul 2022 20:31:17 +0900 Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
> syzbot is reporting GFP_KERNEL allocation with oom_lock held when
> reporting memcg OOM [1]. If this allocation triggers the global OOM
> situation then the system can livelock because the GFP_KERNEL allocation
> with oom_lock held cannot trigger the global OOM killer because
> __alloc_pages_may_oom() fails to hold oom_lock.
>
> Fix this problem by removing the allocation from memory_stat_format()
> completely, and pass static buffer when calling from memcg OOM path.
>
> Note that the caller holding filesystem lock was the trigger for syzbot
> to report this locking dependency. Doing GFP_KERNEL allocation with
> filesystem lock held can deadlock the system even without involving OOM
> situation.
I used the above as the new changelog text.
prev parent reply other threads:[~2022-07-26 18:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220725220032.B4C30C341C8@smtp.kernel.org>
2022-07-26 8:14 ` Michal Hocko
2022-07-26 11:31 ` Tetsuo Handa
2022-07-26 12:04 ` Michal Hocko
2022-07-26 18:50 ` Andrew Morton [this message]
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