diff options
author | Shakeel Butt | 2019-02-01 14:20:54 -0800 |
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committer | Linus Torvalds | 2019-02-01 15:46:23 -0800 |
commit | cefc7ef3c87d02fc9307835868ff721ea12cc597 (patch) | |
tree | 30f0e08427a5ee41babfa097ee6df4bf389c2659 /lib | |
parent | b13bc35193d9e7a8c050a24928ca5c9e7c9a009b (diff) |
mm, oom: fix use-after-free in oom_kill_process
Syzbot instance running on upstream kernel found a use-after-free bug in
oom_kill_process. On further inspection it seems like the process
selected to be oom-killed has exited even before reaching
read_lock(&tasklist_lock) in oom_kill_process(). More specifically the
tsk->usage is 1 which is due to get_task_struct() in oom_evaluate_task()
and the put_task_struct within for_each_thread() frees the tsk and
for_each_thread() tries to access the tsk. The easiest fix is to do
get/put across the for_each_thread() on the selected task.
Now the next question is should we continue with the oom-kill as the
previously selected task has exited? However before adding more
complexity and heuristics, let's answer why we even look at the children
of oom-kill selected task? The select_bad_process() has already selected
the worst process in the system/memcg. Due to race, the selected
process might not be the worst at the kill time but does that matter?
The userspace can use the oom_score_adj interface to prefer children to
be killed before the parent. I looked at the history but it seems like
this is there before git history.
Link: http://lkml.kernel.org/r/20190121215850.221745-1-shakeelb@google.com
Reported-by: syzbot+7fbbfa368521945f0e3d@syzkaller.appspotmail.com
Fixes: 6b0c81b3be11 ("mm, oom: reduce dependency on tasklist_lock")
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
0 files changed, 0 insertions, 0 deletions