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);
}
