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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/huge_memory: fix folio split check for anon folios in swapcache. 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Fix the check. > > Please describe the possible userspace-visible effects of the bug > especially when proposing a -stable backport. Splitting anon folios in swapcache to non-zero order can cause data corruption since swapcache only support PMD order and order-0 entries. This can happen when one use split_huge_pages under debugfs to split anon folios in swapcache. > >> Fixes: 58729c04cf10 ("mm/huge_memory: add buddy allocator like (non-un= iform) folio_split()") >> Reported-by: "David Hildenbrand (Red Hat)" >> Closes: https://lore.kernel.org/all/dc0ecc2c-4089-484f-917f-920fdca4c8= 98@kernel.org/ > > I was hopeful, but that's "from code inspection". In-tree callers do not perform such an illegal operation. Only debugfs interface could trigger it. I will put adding a test case on my TODO list. > >> Cc: stable@vger.kernel.org >> Signed-off-by: Zi Yan Best Regards, Yan, Zi