# CVE-2026-89490

## Summary

- **CVE ID:** CVE-2026-89490
- **Severity:** UNKNOWN
- **CVSS Score:** 0
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 16, 2026

## Description

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.

## Affected Products

- Linux — Linux (ccd979bdbce9fba8412beb3f1de68a9d0171b12c)
- Linux — Linux (2.6.16)
- Linux — Linux (0)
- Linux — Linux (6.12.109)
- Linux — Linux (6.18.50)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)
- Linux — Linux (5.10.270)
- Linux — Linux (5.15.221)
- Linux — Linux (6.1.188)
- Linux — Linux (6.6.157)

## References

- [CNA](https://git.kernel.org/stable/c/1001fb3b69a11eaa0dc7c7428f6edfa48b88997a)
- [CNA](https://git.kernel.org/stable/c/c0c165487a2ea5a37ddcdab4259157b7a527129c)
- [CNA](https://git.kernel.org/stable/c/b53e2b271eeb6040c2a4a78230c570dc41cdcfa4)
- [CNA](https://git.kernel.org/stable/c/a63308ab426f3a3c7e33b02c150ea59054620261)
- [CNA](https://git.kernel.org/stable/c/c28dc3407937aa8f225942538cd585c9b28ea65a)
- [CNA](https://git.kernel.org/stable/c/94569154ba49f5f85645d2019c8e206213d8404e)
- [CNA](https://git.kernel.org/stable/c/1ae7029823ae4c91664cb32eec7fb8dd5e1a337a)
- [CNA](https://git.kernel.org/stable/c/f9dd5cad8d09110ddff2db1fe756aae93c7552ff)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.18%
- **EPSS Percentile:** 7.4

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._