A couple of OOM killer races

[Richard Hayden]

Hi all,

It appears there is no protection in badness() (called by 
out_of_memory() for each process) when it reads p->mm->total_vm. Another 
processor (or a kernel preemption) could presumably run do_exit and then 
exit_mm, freeing the process in question's reference to its mm just 
after the (!p->mm) check but before it reads p->mm->total_vm, making the 
latter reference a null pointer reference.

Also there appears to be no protection when we set p->time_slice in 
__oom_kill_task(). Am I right in thinking that this field should be 
protected by the appropriate runqueue lock, at least this is what 
scheduler_tick() seems to use?

Have I missed anything?

Best regards,

Richard Hayden.

		
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