From: Michal Hocko <mhocko@kernel.org>
To: brookxu <brookxu.cn@gmail.com>
Cc: 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: [PATCH] memcg: fix NULL pointer dereference in __mem_cgroup_usage_unregister_event
Date: Thu, 5 Mar 2020 10:24:47 +0100 [thread overview]
Message-ID: <20200305092447.GQ16139@dhcp22.suse.cz> (raw)
In-Reply-To: <5ee35fe7-2a90-ae71-9100-3f2833cbf252@gmail.com>
Thank you for the report!
On Thu 05-03-20 13:52:03, brookxu wrote:
> One eventfd monitors multiple memory thresholds of cgroup, closing it, the
> system will delete related events. Before all events are deleted, another
> eventfd monitors the cgroup's memory threshold.
Could you describe the race scenario please? Ideally
>
> As a result, thresholds->primary[] is not empty, but thresholds->sparse[]
> is NULL, __mem_cgroup_usage_unregister_event() leading to a crash:
>
> [ 138.925809] BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
> [ 138.926817] IP: [<ffffffff8116c9b7>] mem_cgroup_usage_unregister_event+0xd7/0x1f0
> [ 138.927701] PGD 73bce067 PUD 76ff3067 PMD 0
> [ 138.928384] Oops: 0002 [#1] SMP
> [ 138.935218] CPU: 1 PID: 14 Comm: kworker/1:0 Not tainted 3.10.107-1-tlinux2-0047 #1
Also you seem to be running a very old kernel. Does the problem exist in
the current Vanilla kernel?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-03-05 9:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-05 5:52 brookxu
2020-03-05 9:24 ` Michal Hocko [this message]
2020-03-05 13:28 ` brookxu
2020-03-05 14:07 ` Michal Hocko
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