This is a note to let you know that I've just added the patch titled mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty_slowpath() to the 6.1-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-memcg-fix-null-pointer-in-mem_cgroup_track_foreign_dirty_slowpath.patch and it can be found in the queue-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From ac86f547ca1002aec2ef66b9e64d03f45bbbfbb9 Mon Sep 17 00:00:00 2001 From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Date: Sun, 29 Jan 2023 12:09:45 +0800 Subject: mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty_slowpath() From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> 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@xxxxxxxxxx Fixes: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Reported-by: Ma Wupeng <mawupeng1@xxxxxxxxxx> Tested-by: Miko Larsson <mikoxyzzz@xxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Cc: Ma Wupeng <mawupeng1@xxxxxxxxxx> Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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); } Patches currently in stable-queue which might be from wangkefeng.wang@xxxxxxxxxx are queue-6.1/mm-memcg-fix-null-pointer-in-mem_cgroup_track_foreign_dirty_slowpath.patch