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ocfs2: fix readdir position truncation on 32-bit kernels

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: ocfs2: fix readdir position truncation on 32-bit kernels In ocfs2_dir_foreach_blk_el(), the directory cookie position is rebuilt with ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1)) | offset; `ctx->pos` is loff_t (signed 64-bit), while `sb->s_blocksize` is unsigned long. On 32-bit kernels unsigned long is 32-bit, so the mask ~(sb->s_blocksize - 1) is computed as a 32-bit unsigned value (e.g. 0xfffff000 for a 4 KiB block size). In the AND expression with the 64-bit `ctx->pos`, that unsigned operand is zero-extended to 64 bits per the usual arithmetic conversions, yielding 0x00000000fffff000. The high 32 bits of `ctx->pos` are silently cleared, even though directory size is allowed to exceed 4 GiB. When readdir() crosses the 4 GiB boundary on a 32-bit kernel the position is reset back into the first 4 GiB block, making the re-validation path re-enumerate already-returned dirents indefinitely. This is ocfs2_dir_foreach_blk_el(), the extent-list readdir path taken for all non-inline directories, so a directory large enough to cross 4 GiB reaches it. This is the same class of bug that commit 3dce5bb82c97 ("exfat: Fix bitwise operation having different size") fixed in exfat, and the fix mirrors the equivalent ext4 fix in this series. Cast the operand to loff_t so the mask is 64-bit before the AND: ctx->pos = (ctx->pos & ~((loff_t)sb->s_blocksize - 1)) | offset; 64-bit kernels are unaffected.

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.270, 5.15.221, 6.1.188, 6.12.109, 6.18.50, 6.6.157, 7.2.4
CVEs
CVE-2026-89490
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 15:17 UTC · Revision 1

Source evidence

ocfs2: fix readdir position truncation on 32-bit kernels

core-osv · Original source

Published 11 Sept 2026, 19:43 UTC

In the Linux kernel, the following vulnerability has been resolved: ocfs2: fix readdir position truncation on 32-bit kernels In ocfs2_dir_foreach_blk_el(), the directory cookie position is rebuilt with ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1)) | offset; `ctx->pos` is loff_t (signed 64-bit), while `sb->s_blocksize` is unsigned long. On 32-bit kernels unsigned long is 32-bit, so the mask ~(sb->s_blocksize - 1) is computed as a 32-bit unsigned value (e.g. 0xfffff000 for a 4 KiB block size). In the AND expression with the 64-bit `ctx->pos`, that unsigned operand is zero-extended to 64 bits per the usual arithmetic conversions, yielding 0x00000000fffff000. The high 32 bits of `ctx->pos` are silently cleared, even though directory size is allowed to exceed 4 GiB. When readdir() crosses the 4 GiB boundary on a 32-bit kernel the position is reset back into the first 4 GiB block, making the re-validation path re-enumerate already-returned dirents indefinitely. This is ocfs2_dir_foreach_blk_el(), the extent-list readdir path taken for all non-inline directories, so a directory large enough to cross 4 GiB reaches it. This is the same class of bug that commit 3dce5bb82c97 ("exfat: Fix bitwise operation having different size") fixed in exfat, and the fix mirrors the equivalent ext4 fix in this series. Cast the operand to loff_t so the mask is 64-bit before the AND: ctx->pos = (ctx->pos & ~((loff_t)sb->s_blocksize - 1)) | offset; 64-bit kernels are unaffected.

osv:CVE-2026-89490

Kernel

Fixed versions: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, 6.18.50, 7.2.4

Complete source record
{
  "id": "b87394a0bae6d857ff192f38da70f8c6f1baeb8ec8ea4f71ecfa9df0e137400d",
  "url": "https://osv.dev/vulnerability/CVE-2026-89490",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ocfs2: fix readdir position truncation on 32-bit kernels",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ocfs2: fix readdir position truncation on 32-bit kernels In ocfs2_dir_foreach_blk_el(), the directory cookie position is rebuilt with ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1)) | offset; `ctx->pos` is loff_t (signed 64-bit), while `sb->s_blocksize` is unsigned long. On 32-bit kernels unsigned long is 32-bit, so the mask ~(sb->s_blocksize - 1) is computed as a 32-bit unsigned value (e.g. 0xfffff000 for a 4 KiB block size). In the AND expression with the 64-bit `ctx->pos`, that unsigned operand is zero-extended to 64 bits per the usual arithmetic conversions, yielding 0x00000000fffff000. The high 32 bits of `ctx->pos` are silently cleared, even though directory size is allowed to exceed 4 GiB. When readdir() crosses the 4 GiB boundary on a 32-bit kernel the position is reset back into the first 4 GiB block, making the re-validation path re-enumerate already-returned dirents indefinitely. This is ocfs2_dir_foreach_blk_el(), the extent-list readdir path taken for all non-inline directories, so a directory large enough to cross 4 GiB reaches it. This is the same class of bug that commit 3dce5bb82c97 (\"exfat: Fix bitwise operation having different size\") fixed in exfat, and the fix mirrors the equivalent ext4 fix in this series. Cast the operand to loff_t so the mask is 64-bit before the AND: ctx->pos = (ctx->pos & ~((loff_t)sb->s_blocksize - 1)) | offset; 64-bit kernels are unaffected.",
    "evidence": "osv:CVE-2026-89490",
    "products": [
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          "evidence": "/affected/1/package/name"
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        "prerequisites": [],
        "fixed_versions": [
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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          {
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            "evidence": "/affected/1/ranges"
          },
          {
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            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.109",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.50",
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            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
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    "severity": "unknown",
    "structured": {
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      "aliases": [
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                  "introduced": "2.6.16"
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                {
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            {
              "type": "ECOSYSTEM",
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            },
            {
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                {
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          "package": {
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      ],
      "modified": "2026-10-28T02:30:29.629983665Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1001fb3b69a11eaa0dc7c7428f6edfa48b88997a",
        "https://git.kernel.org/stable/c/1ae7029823ae4c91664cb32eec7fb8dd5e1a337a",
        "https://git.kernel.org/stable/c/94569154ba49f5f85645d2019c8e206213d8404e",
        "https://git.kernel.org/stable/c/a63308ab426f3a3c7e33b02c150ea59054620261",
        "https://git.kernel.org/stable/c/b53e2b271eeb6040c2a4a78230c570dc41cdcfa4",
        "https://git.kernel.org/stable/c/c0c165487a2ea5a37ddcdab4259157b7a527129c",
        "https://git.kernel.org/stable/c/c28dc3407937aa8f225942538cd585c9b28ea65a",
        "https://git.kernel.org/stable/c/f9dd5cad8d09110ddff2db1fe756aae93c7552ff",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89490.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89490",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89490.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89490",
        "evidence": "/id"
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    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 496741,
  "published_at": "2026-09-11T19:43:42.808+00:00"
}