linux-kernel - Re: [PATCH 1/2] Revert "vmalloc: back off when the current task is killed"

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Date:   Fri, 6 Oct 2017 22:51:31 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Alan Cox <alan@...yncelyn.cymru>,
        Christoph Hellwig <hch@....de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH 1/2] Revert "vmalloc: back off when the current task is
 killed"

On Sat, Oct 07, 2017 at 11:21:26AM +0900, Tetsuo Handa wrote:
> On 2017/10/05 19:36, Tetsuo Handa wrote:
> > I don't want this patch backported. If you want to backport,
> > "s/fatal_signal_pending/tsk_is_oom_victim/" is the safer way.
> 
> If you backport this patch, you will see "complete depletion of memory reserves"
> and "extra OOM kills due to depletion of memory reserves" using below reproducer.
> 
> ----------
> #include <linux/module.h>
> #include <linux/slab.h>
> #include <linux/oom.h>
> 
> static char *buffer;
> 
> static int __init test_init(void)
> {
> 	set_current_oom_origin();
> 	buffer = vmalloc((1UL << 32) - 480 * 1048576);

That's not a reproducer, that's a kernel module. It's not hard to
crash the kernel from within the kernel.