{"id":"CVE-2024-49873","summary":"mm/filemap: fix filemap_get_folios_contig THP panic","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/filemap: fix filemap_get_folios_contig THP panic\n\nPatch series \"memfd-pin huge page fixes\".\n\nFix multiple bugs that occur when using memfd_pin_folios with hugetlb\npages and THP.  The hugetlb bugs only bite when the page is not yet\nfaulted in when memfd_pin_folios is called.  The THP bug bites when the\nstarting offset passed to memfd_pin_folios is not huge page aligned.  See\nthe commit messages for details.\n\n\nThis patch (of 5):\n\nmemfd_pin_folios on memory backed by THP panics if the requested start\noffset is not huge page aligned:\n\nBUG: kernel NULL pointer dereference, address: 0000000000000036\nRIP: 0010:filemap_get_folios_contig+0xdf/0x290\nRSP: 0018:ffffc9002092fbe8 EFLAGS: 00010202\nRAX: 0000000000000002 RBX: 0000000000000002 RCX: 0000000000000002\n\nThe fault occurs here, because xas_load returns a folio with value 2:\n\n    filemap_get_folios_contig()\n        for (folio = xas_load(&xas); folio && xas.xa_index \u003c= end;\n                        folio = xas_next(&xas)) {\n                ...\n                if (!folio_try_get(folio))   \u003c-- BOOM\n\n\"2\" is an xarray sibling entry.  We get it because memfd_pin_folios does\nnot round the indices passed to filemap_get_folios_contig to huge page\nboundaries for THP, so we load from the middle of a huge page range see a\nsibling.  (It does round for hugetlbfs, at the is_file_hugepages test).\n\nTo fix, if the folio is a sibling, then return the next index as the\nstarting point for the next call to filemap_get_folios_contig.","modified":"2026-03-20T12:38:08.618864Z","published":"2024-10-21T18:01:14.108Z","related":["USN-7276-1","USN-7277-1","openSUSE-SU-2024:14500-1","openSUSE-SU-2025:14705-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/49xxx/CVE-2024-49873.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/570dd14bfecf281fa467c80f8ec92b26370ee36a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c225c4f6056b46a8a5bf2ed35abf17a2d6887691"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/49xxx/CVE-2024-49873.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-49873"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"89c1905d9c140372b7f50ef48f42378cf85d9bc5"},{"fixed":"570dd14bfecf281fa467c80f8ec92b26370ee36a"},{"fixed":"c225c4f6056b46a8a5bf2ed35abf17a2d6887691"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2024-49873.json"}}],"schema_version":"1.7.5"}