GHSA-FFM2-4XXC-M4VX

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

nilfs2: fix slab-out-of-bounds in nilfs_direct_propagate after truncation

Shuangpeng Bai reported that KASAN detected a slab-out-of-bounds error in nilfs_direct_propagate() during testing.

Analysis revealed that after truncating a file, a node block immediately below the B-tree root was not deleted. Instead, it remained in the B-tree node cache in a dirty state. The log writer subsequently detected this block and incorrectly invoked nilfs_direct_propagate() on it, which is designed to handle only data blocks in direct mapping.

B-tree nodes in the cache are managed by virtual block numbers, and their logical keys typically exceed the range expected by direct mapping. Consequently, processing such a node as a direct mapping entry triggers a slab-out-of-bounds access.

The root cause is that when a B-tree mapping collapses into a direct mapping during truncation, an intermediate node block pointed to by the root node is left behind as garbage instead of being explicitly deleted.

This resolves the issue by adding a nilfs_btree_discard() operation to delete the remaining intermediate node block during the conversion. A 'deform' flag is added to the bop_delete interface to explicitly signal that the deletion is part of a mapping transformation. This allows the B-tree mapping implementation to perform the necessary cleanup and discarding of the residual node structure that would be otherwise be left orphaned after the transition.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-89723"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:20:01Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnilfs2: fix slab-out-of-bounds in nilfs_direct_propagate after truncation\n\nShuangpeng Bai reported that KASAN detected a slab-out-of-bounds error\nin nilfs_direct_propagate() during testing.\n\nAnalysis revealed that after truncating a file, a node block immediately\nbelow the B-tree root was not deleted.  Instead, it remained in the B-tree\nnode cache in a dirty state.  The log writer subsequently detected this\nblock and incorrectly invoked nilfs_direct_propagate() on it, which is\ndesigned to handle only data blocks in direct mapping.\n\nB-tree nodes in the cache are managed by virtual block numbers, and their\nlogical keys typically exceed the range expected by direct mapping.\nConsequently, processing such a node as a direct mapping entry triggers\na slab-out-of-bounds access.\n\nThe root cause is that when a B-tree mapping collapses into a direct\nmapping during truncation, an intermediate node block pointed to by the\nroot node is left behind as garbage instead of being explicitly deleted.\n\nThis resolves the issue by adding a nilfs_btree_discard() operation\nto delete the remaining intermediate node block during the conversion.\nA \u0027deform\u0027 flag is added to the bop_delete interface to explicitly signal\nthat the deletion is part of a mapping transformation.  This allows the\nB-tree mapping implementation to perform the necessary cleanup and\ndiscarding of the residual node structure that would be otherwise be left\norphaned after the transition.",
  "id": "GHSA-ffm2-4xxc-m4vx",
  "modified": "2026-09-14T15:32:35Z",
  "published": "2026-09-11T21:31:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89723"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/28362e8ce51377afdec1782e661e808328a10514"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/39005fd1ce654ffdecacddc406b9a038efe606e6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/448636c745a3f3b8582a0b8ce718c890a11c0fa9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/45662dedb8f272ef7f16e69f13424c4bd0399240"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4a1bb1f9f24a935c9b3f4fbf98012fa6d4ad826d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5d3783c451a546373662ee11ec17019273e68034"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b313edfbc0c2a60f7ce09b2e81ee71909ab8ddaf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bf49e6f6ddc12445a0330708b365de6458085980"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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