GHSA-3JG7-R7PG-8654
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32In 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.
{
"affected": [],
"aliases": [
"CVE-2026-89490"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:30Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nocfs2: fix readdir position truncation on 32-bit kernels\n\nIn ocfs2_dir_foreach_blk_el(), the directory cookie position is\nrebuilt with\n\n\tctx-\u003epos = (ctx-\u003epos \u0026 ~(sb-\u003es_blocksize - 1)) | offset;\n\n`ctx-\u003epos` is loff_t (signed 64-bit), while `sb-\u003es_blocksize` is\nunsigned long. On 32-bit kernels unsigned long is 32-bit, so the mask\n\n\t~(sb-\u003es_blocksize - 1)\n\nis computed as a 32-bit unsigned value (e.g. 0xfffff000 for a 4 KiB\nblock size). In the AND expression with the 64-bit `ctx-\u003epos`, that\nunsigned operand is zero-extended to 64 bits per the usual arithmetic\nconversions, yielding 0x00000000fffff000. The high 32 bits of\n`ctx-\u003epos` are silently cleared, even though directory size is\nallowed to exceed 4 GiB.\n\nWhen readdir() crosses the 4 GiB boundary on a 32-bit kernel the\nposition is reset back into the first 4 GiB block, making the\nre-validation path re-enumerate already-returned dirents indefinitely.\n\nThis is ocfs2_dir_foreach_blk_el(), the extent-list readdir path taken\nfor all non-inline directories, so a directory large enough to cross\n4 GiB reaches it.\n\nThis is the same class of bug that commit 3dce5bb82c97 (\"exfat: Fix\nbitwise operation having different size\") fixed in exfat, and the\nfix mirrors the equivalent ext4 fix in this series. Cast the operand\nto loff_t so the mask is 64-bit before the AND:\n\n\tctx-\u003epos = (ctx-\u003epos \u0026 ~((loff_t)sb-\u003es_blocksize - 1)) | offset;\n\n64-bit kernels are unaffected.",
"id": "GHSA-3jg7-r7pg-8654",
"modified": "2026-09-14T15:32:26Z",
"published": "2026-09-11T21:31:28Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89490"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1001fb3b69a11eaa0dc7c7428f6edfa48b88997a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1ae7029823ae4c91664cb32eec7fb8dd5e1a337a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/94569154ba49f5f85645d2019c8e206213d8404e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a63308ab426f3a3c7e33b02c150ea59054620261"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b53e2b271eeb6040c2a4a78230c570dc41cdcfa4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c0c165487a2ea5a37ddcdab4259157b7a527129c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c28dc3407937aa8f225942538cd585c9b28ea65a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f9dd5cad8d09110ddff2db1fe756aae93c7552ff"
}
],
"schema_version": "1.4.0",
"severity": []
}
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