On Sun, 2023-01-29 at 12:09 +0800, Kefeng Wang wrote:
> 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.
>
> Reported-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
> Fixes: 97b27821b485 ("writeback, memcg: Implement foreign dirty
> flushing")
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> ---
> resend: correct function name
> 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 eb6e5b18e1ad..35478695cabf 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1688,10 +1688,13 @@ 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);
> }
>
Might want to Cc linux-stable.
Tested-by: Miko Larsson <mikoxyzzz@xxxxxxxxx>
--
~miko
