syzbot is reporting fs_reclaim allocation with oom_lock held [1]. We must make sure that such allocation won't hit __alloc_pages_may_oom() path which will retry forever if oom_lock is already held. I choose GFP_ATOMIC than GFP_NOWAIT, for since global OOM situation will likely be avoided by killing some process in memcg, and memory will be released after printk(), trying a little hard will be acceptable. Link: https://syzkaller.appspot.com/bug?extid=2d2aeadc6ce1e1f11d45 [1] Reported-by: syzbot <syzbot+2d2aeadc6ce1e1f11d45@xxxxxxxxxxxxxxxxxxxxxxxxx> Fixes: c8713d0b23123759 ("mm: memcontrol: dump memory.stat during cgroup OOM") Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 618c366a2f07..11cd900729b9 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1465,7 +1465,8 @@ static char *memory_stat_format(struct mem_cgroup *memcg) struct seq_buf s; int i; - seq_buf_init(&s, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE); + /* Caller might be holding oom_lock. */ + seq_buf_init(&s, kmalloc(PAGE_SIZE, GFP_ATOMIC), PAGE_SIZE); if (!s.buffer) return NULL; -- 2.18.4
