Messages in this thread | | | Date | Mon, 30 Jan 2023 20:20:16 +0800 | Subject | Re: [PATCH] mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty() | From | Kefeng Wang <> |
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On 2023/1/30 16:48, Michal Hocko wrote: > On Mon 30-01-23 09:16:13, Kefeng Wang wrote: >> >> >> On 2023/1/30 5:48, Andrew Morton wrote: >>> On Sun, 29 Jan 2023 10:44:51 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote: >>> >>>> As commit 18365225f044 ("hwpoison, memcg: forcibly uncharge LRU pages"), >>> >>> Merged in 2017. >>> >>>> 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() to >>>> fix it. >>>> >>>> Reported-by: Ma Wupeng <mawupeng1@huawei.com> >>>> Fixes: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") >>> >>> Merged in 2019. >>> ... > > Just to make sure I understand. The page has been hwpoisoned, uncharged > but stayed in the page cache so a next page fault on the address has blowned > up? > > Say we address the NULL memcg case. What is the resulting behavior? > Doesn't userspace access a poisoned page and get a silend memory > corruption?
+ Yang Shi
Check previous link[1], seems that it is a known issue, and there is a TODO list for storage backed filesystems from Yang.
[1] https://lore.kernel.org/all/20211020210755.23964-6-shy828301@gmail.com/T/#m1d40559ca2dcf94396df5369214288f69dec379b
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