GHSA-WJ4M-W3QM-XPCH
Vulnerability from github – Published: 2026-03-04 15:30 – Updated: 2026-06-02 15:31In 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.
{
"affected": [],
"aliases": [
"CVE-2026-23238"
],
"database_specific": {
"cwe_ids": [
"CWE-617"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-04T15:16:14Z",
"severity": "MODERATE"
},
"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": "2026-06-02T15:31:53Z",
"published": "2026-03-04T15:30:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23238"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-253495.html"
},
{
"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": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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