From: Kefeng Wang wangkefeng.wang@huawei.com
commit ac86f547ca1002aec2ef66b9e64d03f45bbbfbb9 upstream.
As commit 18365225f044 ("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: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com Reported-by: Ma Wupeng mawupeng1@huawei.com Tested-by: Miko Larsson mikoxyzzz@gmail.com Acked-by: Michal Hocko mhocko@suse.com Cc: Jan Kara jack@suse.cz Cc: Jens Axboe axboe@kernel.dk Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Ma Wupeng mawupeng1@huawei.com Cc: Naoya Horiguchi naoya.horiguchi@nec.com Cc: Shakeel Butt shakeelb@google.com Cc: Tejun Heo tj@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/memcontrol.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1655,10 +1655,13 @@ void mem_cgroup_track_foreign_dirty_slow 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); }