CVE-2026-89836 (GCVE-0-2026-89836)
Vulnerability from cvelistv5
Published
2026-09-16 10:31
Modified
2026-10-19 08:53
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix folio_nr_pages() race after put in large folio invalidate Our v6.18 based Android system is continuely suffering livelock and bad page stat as shown in[1] which related to broken xarray slot status. By investigating big folio operations within f2fs, we find below races and fix it by get the nr_pages before drop the refcount and folio_lock. f2fs_get_read_data_folio() calls f2fs_folio_put() before folio_nr_pages() when invalidating a large folio from the page cache. That unlocks the folio and drops the caller reference, leaving a window where a concurrent truncate or folio split can shrink the compound folio or free it before the invalidate range is computed. An undersized range then leaves split sub-folios in mapping->i_pages, which can later interact badly with truncate and reclaim (stale xarray entries and bad page state when folio->mapping no longer matches the mapping being truncated). [1] PID: 2594 TASK: ffffff8169b81580 CPU: 7 COMMAND: "Thread-3" #0 [ffffffc08ef2b8a0] xas_load at ffffffe52d1f42a4 #1 [ffffffc08ef2b900] find_get_entries at ffffffe52c185798 #2 [ffffffc08ef2bb60] truncate_inode_pages_range at ffffffe52c19e83c #3 [ffffffc08ef2bbc0] truncate_inode_pages_final at ffffffe52c19ec2c #4 [ffffffc08ef2bc20] f2fs_evict_inode at ffffffe52c4c8400 #5 [ffffffc08ef2bcc0] evict at ffffffe52c2de9f4 #6 [ffffffc08ef2bd00] iput at ffffffe52c2db1b4 #7 [ffffffc08ef2bd30] dentry_unlink_inode at ffffffe52c2d7204 #8 [ffffffc08ef2bd50] __dentry_kill at ffffffe52c2d3dcc #9 [ffffffc08ef2bd80] dput at ffffffe52c2d3c3c #10 [ffffffc08ef2bda0] __fput at ffffffe52c2b0a7c #11 [ffffffc08ef2bde0] ____fput at ffffffe52c2b1034 #12 [ffffffc08ef2bdf0] task_work_run at ffffffe52beea200 #13 [ffffffc08ef2be20] exit_to_user_mode_loop at ffffffe52bfbc17c #14 [ffffffc08ef2be80] el0_svc at ffffffe52d1f8e54 #15 [ffffffc08ef2beb0] el0t_64_sync_handler at ffffffe52d1f8d10
References
Impacted products
Vendor Product Version
Linux Linux Version: 05e65c14ea59a401cec4284e9d612f9d5dc1b3f8
Version: 05e65c14ea59a401cec4284e9d612f9d5dc1b3f8
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/f2fs/data.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "cc34df18da92f68f9b384c3ae95ad64be46cb5ee",
              "status": "affected",
              "version": "05e65c14ea59a401cec4284e9d612f9d5dc1b3f8",
              "versionType": "git"
            },
            {
              "lessThan": "0dab71381f1b4d12dc2056f8bd5aaa9d93ce9082",
              "status": "affected",
              "version": "05e65c14ea59a401cec4284e9d612f9d5dc1b3f8",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/f2fs/data.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.0"
            },
            {
              "lessThan": "7.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.5",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix folio_nr_pages() race after put in large folio invalidate\n\nOur v6.18 based Android system is continuely suffering livelock and bad\npage stat as shown in[1] which related to broken xarray slot status. By\ninvestigating big folio operations within f2fs, we find below races and\nfix it by get the nr_pages before drop the refcount and folio_lock.\n\nf2fs_get_read_data_folio() calls f2fs_folio_put() before\nfolio_nr_pages() when invalidating a large folio from the page cache.\nThat unlocks the folio and drops the caller reference, leaving a window\nwhere a concurrent truncate or folio split can shrink the compound folio\nor free it before the invalidate range is computed. An undersized range\nthen leaves split sub-folios in mapping-\u003ei_pages, which can later\ninteract badly with truncate and reclaim (stale xarray entries and bad\npage state when folio-\u003emapping no longer matches the mapping being\ntruncated).\n\n[1]\nPID: 2594     TASK: ffffff8169b81580  CPU: 7    COMMAND: \"Thread-3\"\n #0 [ffffffc08ef2b8a0] xas_load at ffffffe52d1f42a4\n #1 [ffffffc08ef2b900] find_get_entries at ffffffe52c185798\n #2 [ffffffc08ef2bb60] truncate_inode_pages_range at ffffffe52c19e83c\n #3 [ffffffc08ef2bbc0] truncate_inode_pages_final at ffffffe52c19ec2c\n #4 [ffffffc08ef2bc20] f2fs_evict_inode at ffffffe52c4c8400\n #5 [ffffffc08ef2bcc0] evict at ffffffe52c2de9f4\n #6 [ffffffc08ef2bd00] iput at ffffffe52c2db1b4\n #7 [ffffffc08ef2bd30] dentry_unlink_inode at ffffffe52c2d7204\n #8 [ffffffc08ef2bd50] __dentry_kill at ffffffe52c2d3dcc\n #9 [ffffffc08ef2bd80] dput at ffffffe52c2d3c3c\n #10 [ffffffc08ef2bda0] __fput at ffffffe52c2b0a7c\n #11 [ffffffc08ef2bde0] ____fput at ffffffe52c2b1034\n #12 [ffffffc08ef2bdf0] task_work_run at ffffffe52beea200\n #13 [ffffffc08ef2be20] exit_to_user_mode_loop at ffffffe52bfbc17c\n #14 [ffffffc08ef2be80] el0_svc at ffffffe52d1f8e54\n #15 [ffffffc08ef2beb0] el0t_64_sync_handler at ffffffe52d1f8d10"
        }
      ],
      "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is in f2fs_get_read_data_folio() on a locally mounted f2fs volume, reached when GC or other f2fs helpers grab a single-page folio while a large folio is cached. f2fs is the Android/embedded userdata filesystem; the path is local syscalls, not a network protocol.\nAC:L - The attacker drives both sides of the race: one thread keeps large folios cached and forces GC via writes into f2fs_balance_fs, while concurrent threads split or reclaim those folios with posix_fadvise(DONTNEED), madvise, or memory pressure in the window after f2fs_folio_put() and before folio_nr_pages().\nPR:L - CAP_LINUX_IMMUTABLE is needed only to set the flag, but Android f2fs /data already has immutable/fsverity files with large folios. An unprivileged app can read them, write its own data to trigger GC without CAP_SYS_ADMIN, and race reclaim; the GC ioctl is optional.\nUI:N - The attacker can populate large folios, force GC, and race folio split or reclaim with their own processes; no separate victim action is required.\nS:U - Page-cache xarray corruption and folio use-after-free stay inside the host kernel; this is local privilege escalation, not a VM, IOMMU, or sandbox boundary crossing.\nC:H - After the put, folio_nr_pages() may run on a split or already-freed folio, and an undersized invalidate leaves stale i_pages xarray entries. That page-cache UAF allows a reused folio to be read as another mapping\u0027s pages, enabling kernel memory disclosure.\nI:H - Stale mapping-\u003ei_pages slots and UAF of compound-folio metadata are heap and page-cache corruption. Reused folios and later truncate or reclaim against the wrong mapping yield write primitives and control-flow hijacking, not only a crash.\nA:H - The reported failure is livelock and bad page state in truncate_inode_pages_range (xas_load/find_get_entries) during inode eviction, i.e. a kernel oops, BUG, or hang with complete loss of availability."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:53:29.553Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/cc34df18da92f68f9b384c3ae95ad64be46cb5ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/0dab71381f1b4d12dc2056f8bd5aaa9d93ce9082"
        }
      ],
      "title": "f2fs: fix folio_nr_pages() race after put in large folio invalidate",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89836",
    "datePublished": "2026-09-16T10:31:10.233Z",
    "dateReserved": "2026-09-11T19:38:34.769Z",
    "dateUpdated": "2026-10-19T08:53:29.553Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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