Re: [PATCH] oom: fix the unsafe proc_oom_score()->badness() call

[David Rientjes]

On Tue, 30 Mar 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.
> 
> Add the pid_alive() check to ensure __unhash_process() was not called.
> 
> Note: I think we shouldn't use ->group_leader, badness() should return
> the same result for any sub-thread. However this is not true currently,
> and I think that ->mm check and list_for_each_entry(p->children) in
> badness are not right.
> 

I think it would be better to just use task and not task->group_leader.
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