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Subject[patch] mm, oom: avoid attempting to kill init sharing same memory
From: Chen Jie <chenjie6@huawei.com>

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@google.com: rewrote changelog]
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Chen Jie <chenjie6@huawei.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
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.

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;


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