From 5d7bace14dd3e55dfa7e8d157e2b2b7ce7ca457b Mon Sep 17 00:00:00 2001 From: Kefeng Wang Date: Wed, 22 Feb 2023 18:20:26 +0800 Subject: [PATCH] mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty_slowpath() mainline inclusion from mainline-v6.2-rc7 commit ac86f547ca1002aec2ef66b9e64d03f45bbbfbb9 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6BYND Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ac86f547ca1002aec2ef66b9e64d03f45bbbfbb9 -------------------------------- 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 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 Conflicts: include/linux/memcontrol.h Signed-off-by: Lu Jialin Reviewed-by: Kefeng Wang Reviewed-by: Wang Weiyang Signed-off-by: Jialin Zhang --- 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 89e4f01c5710..600cda4ea1be 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1873,10 +1873,13 @@ void mem_cgroup_track_foreign_dirty_slowpath(struct page *page, static inline void mem_cgroup_track_foreign_dirty(struct page *page, struct bdi_writeback *wb) { + struct mem_cgroup *memcg; + if (mem_cgroup_disabled()) return; - if (unlikely(&page_memcg(page)->css != wb->memcg_css)) + memcg = page_memcg(page); + if (unlikely(memcg && &memcg->css != wb->memcg_css)) mem_cgroup_track_foreign_dirty_slowpath(page, wb); } -- GitLab