From 786235eeba0e1e85e5cbbb9f97d1087ad03dfa21 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Tue, 12 Nov 2013 15:06:45 -0800
Subject: [PATCH] kthread: make kthread_create() killable

Any user process callers of wait_for_completion() except global init
process might be chosen by the OOM killer while waiting for completion()
call by some other process which does memory allocation.  See
CVE-2012-4398 "kernel: request_module() OOM local DoS" can happen.

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.

kthread_create() is one of such users and this patch fixes the problem
for kthreadd by making kthread_create() killable - the same approach
used for fixing CVE-2012-4398.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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