ghsa-f7p4-h976-ch7q
Vulnerability from github
Published
2025-09-11 18:35
Modified
2025-09-11 18:35
Details

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

btrfs: qgroup: fix race between quota disable and quota rescan ioctl

There's a race between a task disabling quotas and another running the rescan ioctl that can result in a use-after-free of qgroup records from the fs_info->qgroup_tree rbtree.

This happens as follows:

1) Task A enters btrfs_ioctl_quota_rescan() -> btrfs_qgroup_rescan();

2) Task B enters btrfs_quota_disable() and calls btrfs_qgroup_wait_for_completion(), which does nothing because at that point fs_info->qgroup_rescan_running is false (it wasn't set yet by task A);

3) Task B calls btrfs_free_qgroup_config() which starts freeing qgroups from fs_info->qgroup_tree without taking the lock fs_info->qgroup_lock;

4) Task A enters qgroup_rescan_zero_tracking() which starts iterating the fs_info->qgroup_tree tree while holding fs_info->qgroup_lock, but task B is freeing qgroup records from that tree without holding the lock, resulting in a use-after-free.

Fix this by taking fs_info->qgroup_lock at btrfs_free_qgroup_config(). Also at btrfs_qgroup_rescan() don't start the rescan worker if quotas were already disabled.

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{
  "affected": [],
  "aliases": [
    "CVE-2025-39759"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-09-11T17:15:39Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: qgroup: fix race between quota disable and quota rescan ioctl\n\nThere\u0027s a race between a task disabling quotas and another running the\nrescan ioctl that can result in a use-after-free of qgroup records from\nthe fs_info-\u003eqgroup_tree rbtree.\n\nThis happens as follows:\n\n1) Task A enters btrfs_ioctl_quota_rescan() -\u003e btrfs_qgroup_rescan();\n\n2) Task B enters btrfs_quota_disable() and calls\n   btrfs_qgroup_wait_for_completion(), which does nothing because at that\n   point fs_info-\u003eqgroup_rescan_running is false (it wasn\u0027t set yet by\n   task A);\n\n3) Task B calls btrfs_free_qgroup_config() which starts freeing qgroups\n   from fs_info-\u003eqgroup_tree without taking the lock fs_info-\u003eqgroup_lock;\n\n4) Task A enters qgroup_rescan_zero_tracking() which starts iterating\n   the fs_info-\u003eqgroup_tree tree while holding fs_info-\u003eqgroup_lock,\n   but task B is freeing qgroup records from that tree without holding\n   the lock, resulting in a use-after-free.\n\nFix this by taking fs_info-\u003eqgroup_lock at btrfs_free_qgroup_config().\nAlso at btrfs_qgroup_rescan() don\u0027t start the rescan worker if quotas\nwere already disabled.",
  "id": "GHSA-f7p4-h976-ch7q",
  "modified": "2025-09-11T18:35:52Z",
  "published": "2025-09-11T18:35:52Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39759"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2fd0f5ceb997f90f4332ccbab6c7e907e6b2d0eb"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7cda0fdde5d9890976861421d207870500f9aace"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b172535ccba12f0cf7d23b3b840989de47fc104d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c38028ce0d0045ca600b6a8345a0ff92bfb47b66"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e1249667750399a48cafcf5945761d39fa584edf"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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