CVE-2026-31648 (GCVE-0-2026-31648)
Vulnerability from cvelistv5
Published
2026-04-24 14:45
Modified
2026-04-27 14:04
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
mm: filemap: fix nr_pages calculation overflow in filemap_map_pages()
When running stress-ng on my Arm64 machine with v7.0-rc3 kernel, I
encountered some very strange crash issues showing up as "Bad page state":
"
[ 734.496287] BUG: Bad page state in process stress-ng-env pfn:415735fb
[ 734.496427] page: refcount:0 mapcount:1 mapping:0000000000000000 index:0x4cf316 pfn:0x415735fb
[ 734.496434] flags: 0x57fffe000000800(owner_2|node=1|zone=2|lastcpupid=0x3ffff)
[ 734.496439] raw: 057fffe000000800 0000000000000000 dead000000000122 0000000000000000
[ 734.496440] raw: 00000000004cf316 0000000000000000 0000000000000000 0000000000000000
[ 734.496442] page dumped because: nonzero mapcount
"
After analyzing this page’s state, it is hard to understand why the
mapcount is not 0 while the refcount is 0, since this page is not where
the issue first occurred. By enabling the CONFIG_DEBUG_VM config, I can
reproduce the crash as well and captured the first warning where the issue
appears:
"
[ 734.469226] page: refcount:33 mapcount:0 mapping:00000000bef2d187 index:0x81a0 pfn:0x415735c0
[ 734.469304] head: order:5 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
[ 734.469315] memcg:ffff000807a8ec00
[ 734.469320] aops:ext4_da_aops ino:100b6f dentry name(?):"stress-ng-mmaptorture-9397-0-2736200540"
[ 734.469335] flags: 0x57fffe400000069(locked|uptodate|lru|head|node=1|zone=2|lastcpupid=0x3ffff)
......
[ 734.469364] page dumped because: VM_WARN_ON_FOLIO((_Generic((page + nr_pages - 1),
const struct page *: (const struct folio *)_compound_head(page + nr_pages - 1), struct page *:
(struct folio *)_compound_head(page + nr_pages - 1))) != folio)
[ 734.469390] ------------[ cut here ]------------
[ 734.469393] WARNING: ./include/linux/rmap.h:351 at folio_add_file_rmap_ptes+0x3b8/0x468,
CPU#90: stress-ng-mlock/9430
[ 734.469551] folio_add_file_rmap_ptes+0x3b8/0x468 (P)
[ 734.469555] set_pte_range+0xd8/0x2f8
[ 734.469566] filemap_map_folio_range+0x190/0x400
[ 734.469579] filemap_map_pages+0x348/0x638
[ 734.469583] do_fault_around+0x140/0x198
......
[ 734.469640] el0t_64_sync+0x184/0x188
"
The code that triggers the warning is: "VM_WARN_ON_FOLIO(page_folio(page +
nr_pages - 1) != folio, folio)", which indicates that set_pte_range()
tried to map beyond the large folio’s size.
By adding more debug information, I found that 'nr_pages' had overflowed
in filemap_map_pages(), causing set_pte_range() to establish mappings for
a range exceeding the folio size, potentially corrupting fields of pages
that do not belong to this folio (e.g., page->_mapcount).
After above analysis, I think the possible race is as follows:
CPU 0 CPU 1
filemap_map_pages() ext4_setattr()
//get and lock folio with old inode->i_size
next_uptodate_folio()
.......
//shrink the inode->i_size
i_size_write(inode, attr->ia_size);
//calculate the end_pgoff with the new inode->i_size
file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1;
end_pgoff = min(end_pgoff, file_end);
......
//nr_pages can be overflowed, cause xas.xa_index > end_pgoff
end = folio_next_index(folio) - 1;
nr_pages = min(end, end_pgoff) - xas.xa_index + 1;
......
//map large folio
filemap_map_folio_range()
......
//truncate folios
truncate_pagecache(inode, inode->i_size);
To fix this issue, move the 'end_pgoff' calculation before
next_uptodate_folio(), so the retrieved folio stays consistent with the
file end to avoid
---truncated---
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: fe601b70eac6cd266e8d7d55030e90a73ed0e339 Version: 743a2753a02e805347969f6f89f38b736850d808 Version: 743a2753a02e805347969f6f89f38b736850d808 Version: 743a2753a02e805347969f6f89f38b736850d808 Version: 743a2753a02e805347969f6f89f38b736850d808 Version: 84ede15f27c06b111d1398dfa80b6fac4b135e34 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"mm/filemap.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "88591194df736a508dd5461ab2167a61e98caac1",
"status": "affected",
"version": "fe601b70eac6cd266e8d7d55030e90a73ed0e339",
"versionType": "git"
},
{
"lessThan": "633ab680c405ac390e6bec5b74aaf46197c837b6",
"status": "affected",
"version": "743a2753a02e805347969f6f89f38b736850d808",
"versionType": "git"
},
{
"lessThan": "576543bedd616254032d4ebe54a90076f9e31740",
"status": "affected",
"version": "743a2753a02e805347969f6f89f38b736850d808",
"versionType": "git"
},
{
"lessThan": "9316a820b9aae07d44469d6485376dad824c5b3f",
"status": "affected",
"version": "743a2753a02e805347969f6f89f38b736850d808",
"versionType": "git"
},
{
"lessThan": "f58df566524ebcdfa394329c64f47e3c9257516e",
"status": "affected",
"version": "743a2753a02e805347969f6f89f38b736850d808",
"versionType": "git"
},
{
"status": "affected",
"version": "84ede15f27c06b111d1398dfa80b6fac4b135e34",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"mm/filemap.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.12"
},
{
"lessThan": "6.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.135",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.82",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.23",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.13",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.135",
"versionStartIncluding": "6.6.117",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.82",
"versionStartIncluding": "6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.23",
"versionStartIncluding": "6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.19.13",
"versionStartIncluding": "6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.0",
"versionStartIncluding": "6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.1.159",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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\u2019s 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\u2019s size.\n\nBy adding more debug information, I found that \u0027nr_pages\u0027 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-\u003e_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-\u003ei_size\n next_uptodate_folio()\n\n .......\n //shrink the inode-\u003ei_size\n i_size_write(inode, attr-\u003eia_size);\n\n //calculate the end_pgoff with the new inode-\u003ei_size\n file_end = DIV_ROUND_UP(i_size_read(mapping-\u003ehost), PAGE_SIZE) - 1;\n end_pgoff = min(end_pgoff, file_end);\n\n ......\n //nr_pages can be overflowed, cause xas.xa_index \u003e 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-\u003ei_size);\n\nTo fix this issue, move the \u0027end_pgoff\u0027 calculation before\nnext_uptodate_folio(), so the retrieved folio stays consistent with the\nfile end to avoid \n---truncated---"
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-04-27T14:04:41.675Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/88591194df736a508dd5461ab2167a61e98caac1"
},
{
"url": "https://git.kernel.org/stable/c/633ab680c405ac390e6bec5b74aaf46197c837b6"
},
{
"url": "https://git.kernel.org/stable/c/576543bedd616254032d4ebe54a90076f9e31740"
},
{
"url": "https://git.kernel.org/stable/c/9316a820b9aae07d44469d6485376dad824c5b3f"
},
{
"url": "https://git.kernel.org/stable/c/f58df566524ebcdfa394329c64f47e3c9257516e"
}
],
"title": "mm: filemap: fix nr_pages calculation overflow in filemap_map_pages()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-31648",
"datePublished": "2026-04-24T14:45:01.728Z",
"dateReserved": "2026-03-09T15:48:24.128Z",
"dateUpdated": "2026-04-27T14:04:41.675Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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