{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-31648", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-31648", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-04-24T14:45:01.728Z", "updatedAt": "2026-10-19T18:56:01.381Z", "importedAt": "2026-10-24T01:58:02.025Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "mm: filemap: fix nr_pages calculation overflow in filemap_map_pages()", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: filemap: fix nr_pages calculation overflow in filemap_map_pages()\n\nWhen running stress-ng on my Arm64 machine with v7.0-rc3 kernel, I\nencountered some very strange crash issues showing up as \"Bad page state\":\n\n\"\n[ 734.496287] BUG: Bad page state in process stress-ng-env pfn:415735fb\n[ 734.496427] page: refcount:0 mapcount:1 mapping:0000000000000000 index:0x4cf316 pfn:0x415735fb\n[ 734.496434] flags: 0x57fffe000000800(owner_2|node=1|zone=2|lastcpupid=0x3ffff)\n[ 734.496439] raw: 057fffe000000800 0000000000000000 dead000000000122 0000000000000000\n[ 734.496440] raw: 00000000004cf316 0000000000000000 0000000000000000 0000000000000000\n[ 734.496442] page dumped because: nonzero mapcount\n\"\n\nAfter analyzing this page’s state, it is hard to understand why the\nmapcount is not 0 while the refcount is 0, since this page is not where\nthe issue first occurred. By enabling the CONFIG_DEBUG_VM config, I can\nreproduce the crash as well and captured the first warning where the issue\nappears:\n\n\"\n[ 734.469226] page: refcount:33 mapcount:0 mapping:00000000bef2d187 index:0x81a0 pfn:0x415735c0\n[ 734.469304] head: order:5 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0\n[ 734.469315] memcg:ffff000807a8ec00\n[ 734.469320] aops:ext4_da_aops ino:100b6f dentry name(?):\"stress-ng-mmaptorture-9397-0-2736200540\"\n[ 734.469335] flags: 0x57fffe400000069(locked|uptodate|lru|head|node=1|zone=2|lastcpupid=0x3ffff)\n......\n[ 734.469364] page dumped because: VM_WARN_ON_FOLIO((_Generic((page + nr_pages - 1),\nconst struct page *: (const struct folio *)_compound_head(page + nr_pages - 1), struct page *:\n(struct folio *)_compound_head(page + nr_pages - 1))) != folio)\n[ 734.469390] ------------[ cut here ]------------\n[ 734.469393] WARNING: ./include/linux/rmap.h:351 at folio_add_file_rmap_ptes+0x3b8/0x468,\nCPU#90: stress-ng-mlock/9430\n[ 734.469551] folio_add_file_rmap_ptes+0x3b8/0x468 (P)\n[ 734.469555] set_pte_range+0xd8/0x2f8\n[ 734.469566] filemap_map_folio_range+0x190/0x400\n[ 734.469579] filemap_map_pages+0x348/0x638\n[ 734.469583] do_fault_around+0x140/0x198\n......\n[ 734.469640] el0t_64_sync+0x184/0x188\n\"\n\nThe code that triggers the warning is: \"VM_WARN_ON_FOLIO(page_folio(page +\nnr_pages - 1) != folio, folio)\", which indicates that set_pte_range()\ntried to map beyond the large folio’s size.\n\nBy adding more debug information, I found that 'nr_pages' had overflowed\nin filemap_map_pages(), causing set_pte_range() to establish mappings for\na range exceeding the folio size, potentially corrupting fields of pages\nthat do not belong to this folio (e.g., page->_mapcount).\n\nAfter above analysis, I think the possible race is as follows:\n\nCPU 0 CPU 1\nfilemap_map_pages() ext4_setattr()\n //get and lock folio with old inode->i_size\n next_uptodate_folio()\n\n .......\n //shrink the inode->i_size\n i_size_write(inode, attr->ia_size);\n\n //calculate the end_pgoff with the new inode->i_size\n file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1;\n end_pgoff = min(end_pgoff, file_end);\n\n ......\n //nr_pages can be overflowed, cause xas.xa_index > end_pgoff\n end = folio_next_index(folio) - 1;\n nr_pages = min(end, end_pgoff) - xas.xa_index + 1;\n\n ......\n //map large folio\n filemap_map_folio_range()\n ......\n //truncate folios\n truncate_pagecache(inode, inode->i_size);\n\nTo fix this issue, move the 'end_pgoff' calculation before\nnext_uptodate_folio(), so the retrieved folio stays consistent with the\nfile end to avoid \n---truncated---", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "fe601b70eac6cd266e8d7d55030e90a73ed0e339", "status": "affected", "versionType": "git", "lessThan": "88591194df736a508dd5461ab2167a61e98caac1" }, { "version": "743a2753a02e805347969f6f89f38b736850d808", "status": "affected", "versionType": "git", "lessThan": "633ab680c405ac390e6bec5b74aaf46197c837b6" }, { "version": "743a2753a02e805347969f6f89f38b736850d808", "status": "affected", "versionType": "git", "lessThan": "576543bedd616254032d4ebe54a90076f9e31740" }, { "version": "743a2753a02e805347969f6f89f38b736850d808", "status": "affected", "versionType": "git", "lessThan": "9316a820b9aae07d44469d6485376dad824c5b3f" }, { "version": "743a2753a02e805347969f6f89f38b736850d808", "status": "affected", "versionType": "git", "lessThan": "f58df566524ebcdfa394329c64f47e3c9257516e" }, { "version": "84ede15f27c06b111d1398dfa80b6fac4b135e34", "status": "affected", "versionType": "git" }, { "version": "6.6.117", "status": "affected", "versionType": "semver", "lessThan": "6.6.135" }, { "version": "6.1.159", "status": "affected", "versionType": "semver", "lessThan": "6.2" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "6.12", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "6.12" }, { "version": "6.6.135", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.82", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.23", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "6.19.13", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.19.*" }, { "version": "7.0", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }