Re: [patch] mm, oom: avoid attempting to kill init sharing same memory

From: Michal Hocko
Date: Thu Dec 03 2015 - 03:12:10 EST


On Wed 02-12-15 15:10:28, David Rientjes wrote:
> From: Chen Jie <chenjie6@xxxxxxxxxx>
>
> It's possible that an oom killed victim shares an ->mm with the init
> process and thus oom_kill_process() would end up trying to kill init as
> well.
>
> This has been shown in practice:
>
> Out of memory: Kill process 9134 (init) score 3 or sacrifice child
> Killed process 9134 (init) total-vm:1868kB, anon-rss:84kB, file-rss:572kB
> Kill process 1 (init) sharing same memory
> ...
> Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009
>
> And this will result in a kernel panic.
>
> If a process is forked by init and selected for oom kill while still
> sharing init_mm, then it's likely this system is in a recoverable state.
> However, it's better not to try to kill init and allow the machine to
> panic due to unkillable processes.
>
> [rientjes@xxxxxxxxxx: rewrote changelog]
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Signed-off-by: Chen Jie <chenjie6@xxxxxxxxxx>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
> I removed stable from this patch since the alternative would most likely
> be to panic the system for no killable processes anyway. There's a very
> small likelihood this patch would allow for a recoverable system.

Agreed.

> mm/oom_kill.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -608,6 +608,8 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
> continue;
> if (unlikely(p->flags & PF_KTHREAD))
> continue;
> + if (!is_global_init(p))
> + continue;
> if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
> continue;
>

--
Michal Hocko
SUSE Labs
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