Re: [PATCH rc1-mm 2/3] coredump: shutdown current process first

[Eric W. Biederman]

Oleg Nesterov <oleg@xxxxxxxxxx> writes:

> On 04/10, Roland McGrath wrote:
>>
>> I would be inclined to restructure the inner loop something like this:
>> 
>> 		p = g;
>> 		while (unlikely(p->mm == NULL)) {
>> 			p = next_thread(p);
>> 			if (p == g)
>> 				break;
>> 		}
>> 		if (p->mm == mm) {
>> 			/*
>> 			 * p->sighand can't disappear, but
>> 			 * may be changed by de_thread()
>> 			 */
>> 			lock_task_sighand(p, &flags);
>> 			zap_process(p);
>> 			unlock_task_sighand(p, &flags);
>> 		}
>
> Yes, I agree, this is much more understandable.

There is one piece of zap_threads that still makes me uncomfortable.

task_lock is used to protect p->mm.
Therefore killing a process based upon p->mm == mm is racy
with respect to sys_unshare I believe if we don't take
task_lock.

Eric
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