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charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 31E2B100017 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: 1y1767nzgxziyjxx9gxd6kd36qmsasia X-HE-Tag: 1675238865-796569 X-HE-Meta: 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 5KcRdU7G IYZUAm5r9RPiJF99oZfS3zxf0ULReiQ/wgwcT0bErfw5pyOAlx0x4z1ns7Mdm9UvI/3vGFRQ0RfJvMlAfPZqA4kU8WJzoR5nSzugyrfn67ANqQj8F71A7IS+KSYayXyohhqusUDMq2WJ4Q0NJuj14ACYjRhN9Vgtv0GG2dbtu4i2lpSwFASslf9CduNHjKj+n2PesUeKLYktqsVhf7UvN34IcQ3TaXer/t7yolG+CWRiWJn+CiuD+RVr459hUZRywvMcIurYj+0bkzxa5EtCd77qZ97OmzU79jWuU3ZXcmCKZkswb6cLaLtxOySv4y6CQRZYVLfZ8W4LLyxWnXIxTXpik9+qVrqzaUbpSqkSZ0uD01ro= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon 30-01-23 11:30:47, Yang Shi wrote: > On Mon, Jan 30, 2023 at 4:20 AM Kefeng Wang wrote: > > > > > > > > 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 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 > > >>>> 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. > > For tmpfs and hugetlbfs, the page cache still stay in page cache, the > later page fault will handle the case gracefully. Other real storage > backed filesystem will have page cache truncated. > > The page cache will be uncharged before truncate. If the truncate > fails, we may end up in this case. This would be a good addendum to the changelog. What would be a typical failure in the truncation path? > > > > > > [1] > > https://lore.kernel.org/all/20211020210755.23964-6-shy828301@gmail.com/T/#m1d40559ca2dcf94396df5369214288f69dec379b -- Michal Hocko SUSE Labs