cve-2024-40950
Vulnerability from cvelistv5
Published
2024-07-12 12:31
Modified
2024-12-19 09:08
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: mm: huge_memory: fix misused mapping_large_folio_support() for anon folios When I did a large folios split test, a WARNING "[ 5059.122759][ T166] Cannot split file folio to non-0 order" was triggered. But the test cases are only for anonmous folios. while mapping_large_folio_support() is only reasonable for page cache folios. In split_huge_page_to_list_to_order(), the folio passed to mapping_large_folio_support() maybe anonmous folio. The folio_test_anon() check is missing. So the split of the anonmous THP is failed. This is also the same for shmem_mapping(). We'd better add a check for both. But the shmem_mapping() in __split_huge_page() is not involved, as for anonmous folios, the end parameter is set to -1, so (head[i].index >= end) is always false. shmem_mapping() is not called. Also add a VM_WARN_ON_ONCE() in mapping_large_folio_support() for anon mapping, So we can detect the wrong use more easily. THP folios maybe exist in the pagecache even the file system doesn't support large folio, it is because when CONFIG_TRANSPARENT_HUGEPAGE is enabled, khugepaged will try to collapse read-only file-backed pages to THP. But the mapping does not actually support multi order large folios properly. Using /sys/kernel/debug/split_huge_pages to verify this, with this patch, large anon THP is successfully split and the warning is ceased.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5df493a99fcf887133cf01d23cd4bebb6d385d3c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6a50c9b512f7734bc356f4bd47885a6f7c98491a
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/5df493a99fcf887133cf01d23cd4bebb6d385d3c
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/6a50c9b512f7734bc356f4bd47885a6f7c98491a
Impacted products
Vendor Product Version
Linux Linux Version: c010d47f107f609b9f4d6a103b6dfc53889049e9
Version: c010d47f107f609b9f4d6a103b6dfc53889049e9
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   Linux Linux Version: 6.9
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