On Tue, 26 Jul 2022 20:31:17 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > syzbot is reporting GFP_KERNEL allocation with oom_lock held when > reporting memcg OOM [1]. If this allocation triggers the global OOM > situation then the system can livelock because the GFP_KERNEL allocation > with oom_lock held cannot trigger the global OOM killer because > __alloc_pages_may_oom() fails to hold oom_lock. > > Fix this problem by removing the allocation from memory_stat_format() > completely, and pass static buffer when calling from memcg OOM path. > > Note that the caller holding filesystem lock was the trigger for syzbot > to report this locking dependency. Doing GFP_KERNEL allocation with > filesystem lock held can deadlock the system even without involving OOM > situation. I used the above as the new changelog text.
