Squashfs: check return result of sb_min_blocksize

{
  "id": "f39db0c5776ccc83cb312f883a6bddc59a1f0aa7e162e2b5b7f36ea83f1e356b",
  "url": "https://osv.dev/vulnerability/CVE-2025-38415",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Squashfs: check return result of sb_min_blocksize",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: Squashfs: check return result of sb_min_blocksize Syzkaller reports an \"UBSAN: shift-out-of-bounds in squashfs_bio_read\" bug. Syzkaller forks multiple processes which after mounting the Squashfs filesystem, issues an ioctl(\"/dev/loop0\", LOOP_SET_BLOCK_SIZE, 0x8000). Now if this ioctl occurs at the same time another process is in the process of mounting a Squashfs filesystem on /dev/loop0, the failure occurs. When this happens the following code in squashfs_fill_super() fails. ---- msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE); msblk->devblksize_log2 = ffz(~msblk->devblksize); ---- sb_min_blocksize() returns 0, which means msblk->devblksize is set to 0. As a result, ffz(~msblk->devblksize) returns 64, and msblk->devblksize_log2 is set to 64. This subsequently causes the UBSAN: shift-out-of-bounds in fs/squashfs/block.c:195:36 shift exponent 64 is too large for 64-bit type 'u64' (aka 'unsigned long long') This commit adds a check for a 0 return by sb_min_blocksize().",
    "evidence": "osv:CVE-2025-38415",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
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    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-38415",
      "aliases": [
        "CVE-2025-38415"
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                  "fixed": "5c51aa862cbeed2f3887f0382a2708956710bd68"
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      "modified": "2026-10-28T02:30:52.340842773Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0aff95d9bc7fb5400ca8af507429c4b067bdb425",
        "https://git.kernel.org/stable/c/295ab18c2dbce8d0ac6ecf7c5187e16e1ac8b282",
        "https://git.kernel.org/stable/c/4f99357dadbf9c979ad737156ad4c37fadf7c56b",
        "https://git.kernel.org/stable/c/549f9e3d7b60d53808c98b9fde49b4f46d0524a5",
        "https://git.kernel.org/stable/c/5c51aa862cbeed2f3887f0382a2708956710bd68",
        "https://git.kernel.org/stable/c/6abf6b78c6fb112eee495f5636ffcc350dd2ce25",
        "https://git.kernel.org/stable/c/734aa85390ea693bb7eaf2240623d41b03705c84",
        "https://git.kernel.org/stable/c/db7096ea160e40d78c67fce52e7cc51bde049497",
        "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html",
        "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38415.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-38415",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38415.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-38415",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 521072,
  "published_at": "2025-07-25T13:32:09.711+00:00"
}