{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:12",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:13",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.12.85-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.19.13-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "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-\u003e_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-\u003ei_size    next_uptodate_folio()                                                            .......                                                           //shrink the inode-\u003ei_size                                                           i_size_write(inode, attr-\u003eia_size);     //calculate the end_pgoff with the new inode-\u003ei_size    file_end = DIV_ROUND_UP(i_size_read(mapping-\u003ehost), PAGE_SIZE) - 1;    end_pgoff = min(end_pgoff, file_end);     ......    //nr_pages can be overflowed, cause xas.xa_index \u003e 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-\u003ei_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---",
  "id": "DEBIAN-CVE-2026-31648",
  "modified": "2026-09-14T16:47:37.369168644Z",
  "published": "2026-04-24T15:16:44.193Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-31648"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-31648"
  ]
}