From 53b2ce0c3b2f5baafa50b57e0d845f25e6eadd2b Mon Sep 17 00:00:00 2001 From: Kefeng Wang Date: Sun, 29 Jan 2023 12:09:45 +0800 Subject: [PATCH] mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty_slowpath() commit ac86f547ca1002aec2ef66b9e64d03f45bbbfbb9 upstream. As commit e25d7d1359d3 ("hwpoison, memcg: forcibly uncharge LRU pages"), hwpoison will forcibly uncharg a LRU hwpoisoned page, the folio_memcg could be NULl, then, mem_cgroup_track_foreign_dirty_slowpath() could occurs a NULL pointer dereference, let's do not record the foreign writebacks for folio memcg is null in mem_cgroup_track_foreign_dirty() to fix it. Link: https://lkml.kernel.org/r/20230129040945.180629-1-wangkefeng.wang@huawei.com Fixes: 0dd05dfabac5 ("writeback, memcg: Implement foreign dirty flushing") Signed-off-by: Kefeng Wang Reported-by: Ma Wupeng Tested-by: Miko Larsson Acked-by: Michal Hocko Cc: Jan Kara Cc: Jens Axboe Cc: Kefeng Wang Cc: Ma Wupeng Cc: Naoya Horiguchi Cc: Shakeel Butt Cc: Tejun Heo Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- include/linux/memcontrol.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index e1644a24009c8..e039763029563 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1655,10 +1655,13 @@ void mem_cgroup_track_foreign_dirty_slowpath(struct folio *folio, static inline void mem_cgroup_track_foreign_dirty(struct folio *folio, struct bdi_writeback *wb) { + struct mem_cgroup *memcg; + if (mem_cgroup_disabled()) return; - if (unlikely(&folio_memcg(folio)->css != wb->memcg_css)) + memcg = folio_memcg(folio); + if (unlikely(memcg && &memcg->css != wb->memcg_css)) mem_cgroup_track_foreign_dirty_slowpath(folio, wb); } -- 2.39.5