Re: can't oom-kill zap the victim's memory?

[Oleg Nesterov]

(off-topic)

On 09/19, Oleg Nesterov wrote:
>
> @@ -570,8 +590,8 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
>  		victim = p;
>  	}
>
> -	/* mm cannot safely be dereferenced after task_unlock(victim) */
>  	mm = victim->mm;
> +	atomic_inc(&mm->mm_count);

Btw, I think we need this change anyway. This is pure theoretical, but
otherwise this task can exit and free its mm_struct right after task_unlock(),
then this mm_struct can be reallocated and used by another task, so we
can't trust the "p->mm == mm" check below.

Oleg.

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