GHSA-WJ4M-W3QM-XPCH

Vulnerability from github – Published: 2026-03-04 15:30 – Updated: 2026-03-04 15:30
VLAI?
Details

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

romfs: check sb_set_blocksize() return value

romfs_fill_super() ignores the return value of sb_set_blocksize(), which can fail if the requested block size is incompatible with the block device's configuration.

This can be triggered by setting a loop device's block size larger than PAGE_SIZE using ioctl(LOOP_SET_BLOCK_SIZE, 32768), then mounting a romfs filesystem on that device.

When sb_set_blocksize(sb, ROMBSIZE) is called with ROMBSIZE=4096 but the device has logical_block_size=32768, bdev_validate_blocksize() fails because the requested size is smaller than the device's logical block size. sb_set_blocksize() returns 0 (failure), but romfs ignores this and continues mounting.

The superblock's block size remains at the device's logical block size (32768). Later, when sb_bread() attempts I/O with this oversized block size, it triggers a kernel BUG in folio_set_bh():

kernel BUG at fs/buffer.c:1582!
BUG_ON(size > PAGE_SIZE);

Fix by checking the return value of sb_set_blocksize() and failing the mount with -EINVAL if it returns 0.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-23238"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-03-04T15:16:14Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nromfs: check sb_set_blocksize() return value\n\nromfs_fill_super() ignores the return value of sb_set_blocksize(), which\ncan fail if the requested block size is incompatible with the block\ndevice\u0027s configuration.\n\nThis can be triggered by setting a loop device\u0027s block size larger than\nPAGE_SIZE using ioctl(LOOP_SET_BLOCK_SIZE, 32768), then mounting a romfs\nfilesystem on that device.\n\nWhen sb_set_blocksize(sb, ROMBSIZE) is called with ROMBSIZE=4096 but the\ndevice has logical_block_size=32768, bdev_validate_blocksize() fails\nbecause the requested size is smaller than the device\u0027s logical block\nsize. sb_set_blocksize() returns 0 (failure), but romfs ignores this and\ncontinues mounting.\n\nThe superblock\u0027s block size remains at the device\u0027s logical block size\n(32768). Later, when sb_bread() attempts I/O with this oversized block\nsize, it triggers a kernel BUG in folio_set_bh():\n\n    kernel BUG at fs/buffer.c:1582!\n    BUG_ON(size \u003e PAGE_SIZE);\n\nFix by checking the return value of sb_set_blocksize() and failing the\nmount with -EINVAL if it returns 0.",
  "id": "GHSA-wj4m-w3qm-xpch",
  "modified": "2026-03-04T15:30:36Z",
  "published": "2026-03-04T15:30:36Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23238"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2c5829cd8fbbc91568c520b666898f57cdcb8cf6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4b71ad7676564a94ec5f7d18298f51e8ae53db73"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9b203b8ddd7359270e8a694d0584743555128e2c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a381f0f61b35c8894b0bd0d6acef2d8f9b08b244"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ab7ad7abb3660c58ffffdf07ff3bb976e7e0afa0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cbd9931e6456822067725354d83446c5bb813030"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f2521ab1f63a8c244f06a080319e5ff9a2e1bd95"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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