GHSA-M9PV-2424-H7VV

Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-19 18:32
VLAI
Details

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

fscrypt: Avoid dynamic allocation in fscrypt_get_devices()

When a blk_crypto_key starts being used or is evicted, fs/crypto/ calls fscrypt_get_devices() to get the filesystem's list of block devices, then iterates over them and calls blk_crypto_config_supported(), blk_crypto_start_using_key(), or blk_crypto_evict_key() on each one.

Currently, the block device pointers are placed in a dynamically allocated array. This dynamic allocation is problematic because:

  • It can fail, especially at the fscrypt_destroy_inline_crypt_key() call site when it's invoked for inode eviction under direct reclaim.

  • fscrypt_destroy_inline_crypt_key() doesn't handle the failure. It just zeroizes and frees the blk_crypto_key without calling blk_crypto_evict_key(). That causes a use-after-free.

For now, let's fix this in the straightforward and easily-backportable way by switching to an on-stack array. Currently the fscrypt multi-device functionality is used only by f2fs, which has a hardcoded limit of 8 block devices. An on-stack array works fine for that.

(Of course, this solution won't scale up to large number of block devices. For that we'd need a different solution, like moving the block device iteration into the filesystem. Or in the case of btrfs, which will only support blk-crypto-fallback, we should make it just call blk-crypto-fallback directly, so the block devices won't be needed.)

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-2026-68147"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-10T13:20:00Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfscrypt: Avoid dynamic allocation in fscrypt_get_devices()\n\nWhen a blk_crypto_key starts being used or is evicted, fs/crypto/ calls\nfscrypt_get_devices() to get the filesystem\u0027s list of block devices,\nthen iterates over them and calls blk_crypto_config_supported(),\nblk_crypto_start_using_key(), or blk_crypto_evict_key() on each one.\n\nCurrently, the block device pointers are placed in a dynamically\nallocated array.  This dynamic allocation is problematic because:\n\n- It can fail, especially at the fscrypt_destroy_inline_crypt_key() call\n  site when it\u0027s invoked for inode eviction under direct reclaim.\n\n- fscrypt_destroy_inline_crypt_key() doesn\u0027t handle the failure.  It\n  just zeroizes and frees the blk_crypto_key without calling\n  blk_crypto_evict_key().  That causes a use-after-free.\n\nFor now, let\u0027s fix this in the straightforward and easily-backportable\nway by switching to an on-stack array.  Currently the fscrypt\nmulti-device functionality is used only by f2fs, which has a hardcoded\nlimit of 8 block devices.  An on-stack array works fine for that.\n\n(Of course, this solution won\u0027t scale up to large number of block\ndevices.  For that we\u0027d need a different solution, like moving the block\ndevice iteration into the filesystem.  Or in the case of btrfs, which\nwill only support blk-crypto-fallback, we should make it just call\nblk-crypto-fallback directly, so the block devices won\u0027t be needed.)",
  "id": "GHSA-m9pv-2424-h7vv",
  "modified": "2026-08-19T18:32:07Z",
  "published": "2026-08-10T15:33:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68147"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4462ac3d90e897dda52ce4b6af2d526ddae835a8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6fe4e4b8259e1330945b5f3c9476e08473b8e0e8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/81ea8e8221853950c47dac7164f27c63a96f8f86"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/97a688563be71ec6fefc071aff69a66c69dbe244"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bab016bb80d74a9d1f7d4121a7fc1cb529b470e0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bc2d630296e0e049210ec05ff08459a6893ae749"
    }
  ],
  "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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