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Tsirkin" Cc: linux-kernel@vger.kernel.org, Miaohe Lin , "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , =?utf-8?q?Eugenio_P=C3=A9rez?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. 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Tsirkin wrote: > TestSetPageHWPoison() is called without zone->lock, so its atomic > update to page->flags can race with non-atomic flag operations > that run under zone->lock in the buddy allocator. > > In particular, __free_pages_prepare() does: > > page->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP; > > This non-atomic read-modify-write, while correctly excluding > __PG_HWPOISON from the mask, can still lose a concurrent > TestSetPageHWPoison if the read happens before the poison bit > is set and the write happens after. Will only get worse if/when > we add more non-atomic flag operations. > > Fix by acquiring zone->lock around TestSetPageHWPoison and > around ClearPageHWPoison in the retry path. This > serializes with all buddy flag manipulation. The cost is > negligible: one lock/unlock in an extremely rare path > (hardware memory errors). > > Note: SetPageHWPoison and TestClearPageHWPoison calls elsewhere > in this file operate on pages already removed from the buddy > allocator or on non-buddy pages (DAX, hugetlb), so they do not > need zone->lock protection. > > Fixes: 6a46079cf57a ("HWPOISON: The high level memory error handler in the VM v7") > Acked-by: Miaohe Lin > Signed-off-by: Michael S. Tsirkin > Assisted-by: Claude:claude-opus-4-6 > --- > > Sending separately as suggested by multiple people. I also added > a Fixes tag. > > > mm/memory-failure.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > Makes sense to me. Thanks. Acked-by: Zi Yan Best Regards, Yan, Zi