linux-kernel - Re: [PATCH] OOM killer: wait for tasks with pending SIGKILL to exit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 9 Sep 2013 18:31:09 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Sergey Dyasly <dserrg@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Michal Hocko <mhocko@...e.cz>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Sha Zhengju <handai.szj@...bao.com>
Subject: Re: [PATCH] OOM killer: wait for tasks with pending SIGKILL to exit

Can't really comment this patch, just one off-topic note...

On 09/09, Sergey Dyasly wrote:
>
> @@ -275,13 +275,16 @@ enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
>  	if (oom_task_origin(task))
>  		return OOM_SCAN_SELECT;
>  
> -	if (task->flags & PF_EXITING && !force_kill) {
> +	if ((task->flags & PF_EXITING || fatal_signal_pending(task)) &&
> +	    !force_kill) {
>  		/*
>  		 * If this task is not being ptraced on exit, then wait for it
>  		 * to finish before killing some other task unnecessarily.
>  		 */
> -		if (!(task->group_leader->ptrace & PT_TRACE_EXIT))
> +		if (!(task->group_leader->ptrace & PT_TRACE_EXIT)) {

can't we finally kill (or fix?) this PT_TRACE_EXIT check?

It was added to fix the exploit I sent. But the patch was wrong,
that exploit could be easily modified to trigger the same problem.

However, now that the coredumping is killable that exploit won't
work, so the original reason has gone away.

So why do we need this check today?

And note that we check ->group_leader, this looks completely wrong.
(again, ->group_leader was used just because the original exploit
 traced the group leader).

David?

Oleg.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/