GHSA-4RVM-HH4P-2JFJ
Vulnerability from github – Published: 2025-09-05 18:31 – Updated: 2025-12-03 21:30In the Linux kernel, the following vulnerability has been resolved:
loop: Avoid updating block size under exclusive owner
Syzbot came up with a reproducer where a loop device block size is changed underneath a mounted filesystem. This causes a mismatch between the block device block size and the block size stored in the superblock causing confusion in various places such as fs/buffer.c. The particular issue triggered by syzbot was a warning in __getblk_slow() due to requested buffer size not matching block device block size.
Fix the problem by getting exclusive hold of the loop device to change its block size. This fails if somebody (such as filesystem) has already an exclusive ownership of the block device and thus prevents modifying the loop device under some exclusive owner which doesn't expect it.
{
"affected": [],
"aliases": [
"CVE-2025-38709"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-09-04T16:15:39Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nloop: Avoid updating block size under exclusive owner\n\nSyzbot came up with a reproducer where a loop device block size is\nchanged underneath a mounted filesystem. This causes a mismatch between\nthe block device block size and the block size stored in the superblock\ncausing confusion in various places such as fs/buffer.c. The particular\nissue triggered by syzbot was a warning in __getblk_slow() due to\nrequested buffer size not matching block device block size.\n\nFix the problem by getting exclusive hold of the loop device to change\nits block size. This fails if somebody (such as filesystem) has already\nan exclusive ownership of the block device and thus prevents modifying\nthe loop device under some exclusive owner which doesn\u0027t expect it.",
"id": "GHSA-4rvm-hh4p-2jfj",
"modified": "2025-12-03T21:30:58Z",
"published": "2025-09-05T18:31:16Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38709"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/139a000d20f2f38ce34296feddd641d730fe1c08"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/457d2c5e112fd08dc1039b1ae39a83ec1782360d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5d67b30aefeb7a949040bbb1b4e3b84c5d29a624"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7e49538288e523427beedd26993d446afef1a6fb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b928438cc87c0bf7ae078e4b7b6e14261e84c5c5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ce8da5d13d8c2a7b30b2fb376a22e8eb1a70b8bb"
}
],
"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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