Re: [PATCH 1/1] oom: fix the unsafe usage of badness() inproc_oom_score()
From: David Rientjes
Date: Thu Apr 01 2010 - 15:04:04 EST
On Thu, 1 Apr 2010, Oleg Nesterov wrote:
> proc_oom_score(task) have a reference to task_struct, but that is all.
> If this task was already released before we take tasklist_lock
> - we can't use task->group_leader, it points to nowhere
> - it is not safe to call badness() even if this task is
> ->group_leader, has_intersects_mems_allowed() assumes
> it is safe to iterate over ->thread_group list.
> - even worse, badness() can hit ->signal == NULL
> Add the pid_alive() check to ensure __unhash_process() was not called.
> Also, use "task" instead of task->group_leader. badness() should return
> the same result for any sub-thread. Currently this is not true, but
> this should be changed anyway.
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Andrew, this is 2.6.34 material and should be backported to stable. It's
not introduced by the recent oom killer rewrite pending in -mm, but it
will require a trivial merge resolution on that work.
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