diff options
| author | Zi Yan <ziy@nvidia.com> | 2025-11-05 11:29:10 -0500 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-11-15 10:52:01 -0800 |
| commit | f1d47cafe513b5552a5b20a7af0936d9070a8a78 (patch) | |
| tree | 3d152d56b8692893af6330b2c85d6c016dc122bc | |
| parent | 3470715e5c22578c6ea4098b256d5a904e12eef2 (diff) | |
mm/huge_memory: fix folio split check for anon folios in swapcache
Both uniform and non uniform split check missed the check to prevent
splitting anon folios in swapcache to non-zero order.
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.
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.
Fix the check.
Link: https://lkml.kernel.org/r/20251105162910.752266-1-ziy@nvidia.com
Fixes: 58729c04cf10 ("mm/huge_memory: add buddy allocator like (non-uniform) folio_split()")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reported-by: "David Hildenbrand (Red Hat)" <david@kernel.org>
Closes: https://lore.kernel.org/all/dc0ecc2c-4089-484f-917f-920fdca4c898@kernel.org/
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/huge_memory.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 323654fb4f8c..2f2a521e5d68 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3522,7 +3522,8 @@ bool non_uniform_split_supported(struct folio *folio, unsigned int new_order, /* order-1 is not supported for anonymous THP. */ VM_WARN_ONCE(warns && new_order == 1, "Cannot split to order-1 folio"); - return new_order != 1; + if (new_order == 1) + return false; } else if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !mapping_large_folio_support(folio->mapping)) { /* @@ -3553,7 +3554,8 @@ bool uniform_split_supported(struct folio *folio, unsigned int new_order, if (folio_test_anon(folio)) { VM_WARN_ONCE(warns && new_order == 1, "Cannot split to order-1 folio"); - return new_order != 1; + if (new_order == 1) + return false; } else if (new_order) { if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !mapping_large_folio_support(folio->mapping)) { |