linux-kernel - Re: [PATCH v3] kthread: Make kthread

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 25 Sep 2013 14:05:02 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
cc:	akpm@...ux-foundation.org, oleg@...hat.com, security@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] kthread: Make kthread_create() killable.

On Wed, 25 Sep 2013, Tetsuo Handa wrote:

> Any users of wait_for_completion() might be chosen by the OOM killer while
> waiting for completion() call by some process which does memory
> allocation.  kthread_create() is one of such users.
> 

Any user process callers of wait_for_completion() you mean.

> When such users are chosen by the OOM killer when they are waiting for
> completion() in TASK_UNINTERRUPTIBLE, the system will be kept stressed
> due to memory starvation because the OOM killer cannot kill such users.
> 

Also results in a livelock if you're running in a memcg and have hit its 
limit.

> Fix this problem for kthreadd by making kthread_create() killable.
> 

There appear to be other potential callers of wait_for_completion() in the 
tree as well that could be holding lots of memory besides 
kthread_create().

Perhaps that's beyond the scope of this particular patch, though.

wait_for_completion() is scary if that completion requires memory that 
cannot be allocated because the caller is killed but uninterruptible.

> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>

Acked-by: David Rientjes <rientjes@...gle.com>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/