GHSA-398P-2VFW-CH77
Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-08-11 21:32In the Linux kernel, the following vulnerability has been resolved:
iommu/amd: Remove latent out-of-bounds access in IOMMU debugfs
In iommu_mmio_write() and iommu_capability_write(), the variables dbg_mmio_offset and dbg_cap_offset are declared as int. However, they are populated using kstrtou32_from_user(). If a user provides a sufficiently large value, it can become a negative integer.
Prior to this patch, the AMD IOMMU debugfs implementation was already protected by different mechanisms.
-
define OFS_IN_SZ 8 ensures the user string <= 8 bytes, so
e.g. 0xffffffff isn't a valid input.
if (cnt > OFS_IN_SZ) return -EINVAL;
- Implicit type promotion in iommu_mmio_write(), dbg_mmio_offset is int and iommu->mmio_phys_end is u64
if (dbg_mmio_offset > iommu->mmio_phys_end - sizeof(u64)) return -EINVAL;
- The show handlers would currently catch the negative number and refuse to perform the read.
Replace kstrtou32_from_user() with kstrtos32_from_user() to parse the input, and check for negative values to explicitly prevent out-of-bounds memory accesses directly in iommu_mmio_write() and iommu_capability_write().
{
"affected": [],
"aliases": [
"CVE-2026-64186"
],
"database_specific": {
"cwe_ids": [
"CWE-125"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-19T16:18:01Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\niommu/amd: Remove latent out-of-bounds access in IOMMU debugfs\n\nIn iommu_mmio_write() and iommu_capability_write(), the variables\ndbg_mmio_offset and dbg_cap_offset are declared as int. However, they\nare populated using kstrtou32_from_user(). If a user provides a\nsufficiently large value, it can become a negative integer.\n\nPrior to this patch, the AMD IOMMU debugfs implementation was already\nprotected by different mechanisms.\n\n1. #define OFS_IN_SZ 8 ensures the user string \u003c= 8 bytes, so\n e.g. 0xffffffff isn\u0027t a valid input.\n\n if (cnt \u003e OFS_IN_SZ)\n return -EINVAL;\n\n2. Implicit type promotion in iommu_mmio_write(), dbg_mmio_offset is int\n and iommu-\u003emmio_phys_end is u64\n\n if (dbg_mmio_offset \u003e iommu-\u003emmio_phys_end - sizeof(u64))\n return -EINVAL;\n\n3. The show handlers would currently catch the negative number and\n refuse to perform the read.\n\nReplace kstrtou32_from_user() with kstrtos32_from_user() to parse the\ninput, and check for negative values to explicitly prevent out-of-bounds\nmemory accesses directly in iommu_mmio_write() and\niommu_capability_write().",
"id": "GHSA-398p-2vfw-ch77",
"modified": "2026-08-11T21:32:24Z",
"published": "2026-07-19T18:31:54Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64186"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/488d2c76bd9f78433a70690d1054bfae3d39a407"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/62f9dfbf1aceae88b03c5ca08f7d36e943939dec"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8dfd3d8d74435344ee8dc9237596959c8b2a6cbe"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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