CVE-2026-90136 (GCVE-0-2026-90136)
Vulnerability from cvelistv5
Published
2026-09-17 16:06
Modified
2026-10-19 08:58
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: platform/x86/amd/hsmp: Reject negative power cap writes in hwmon hsmp_hwmon_write() takes the user-supplied hwmon value as a signed long and assigns "val / MICROWATT_PER_MILLIWATT" to msg.args[0], which is a __u32. MICROWATT_PER_MILLIWATT is an unsigned long, so a negative write to power1_cap (e.g. "echo -1 > power1_cap") is first converted to a huge unsigned value by the division and then stored into the u32 argument. As a result a nonsensical, multi-gigawatt socket power limit is sent to the SMU via HSMP_SET_SOCKET_POWER_LIMIT instead of the write being rejected. Reject negative values with -EINVAL before the conversion. Tested with HSMP enabled: CAP=$(dirname $(grep -l amd_hsmp_hwmon \ /sys/class/hwmon/hwmon*/name | head -1))/power1_cap # negative write echo -1000000 > $CAP ; echo "ret=$?" # valid positive write must still work echo 400000000 > $CAP ; echo "ret=$?" Before: # echo -1000000 > $CAP ; echo "ret=$?" ret=0 <- accepted; bogus limit sent to SMU # echo 400000000 > $CAP ; echo "ret=$?" ret=0 After: # echo -1000000 > $CAP ; echo "ret=$?" bash: echo: write error: Invalid argument ret=1 <- rejected with -EINVAL # echo 400000000 > $CAP ; echo "ret=$?" ret=0 <- valid write still works
References
Impacted products
Vendor Product Version
Linux Linux Version: 92c025db52bb94a032eb3d473bb81e62c19ddbd3
Version: 92c025db52bb94a032eb3d473bb81e62c19ddbd3
Version: 92c025db52bb94a032eb3d473bb81e62c19ddbd3
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/platform/x86/amd/hsmp/hwmon.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "2c09cadec116eba3fdbcb5d8d8641f6777d4a11f",
              "status": "affected",
              "version": "92c025db52bb94a032eb3d473bb81e62c19ddbd3",
              "versionType": "git"
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              "lessThan": "1b0a3d915320f1600e5ff43f8bc21b73118480b8",
              "status": "affected",
              "version": "92c025db52bb94a032eb3d473bb81e62c19ddbd3",
              "versionType": "git"
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          "product": "Linux",
          "programFiles": [
            "drivers/platform/x86/amd/hsmp/hwmon.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.16"
            },
            {
              "lessThan": "6.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.52",
                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "6.16",
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                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nplatform/x86/amd/hsmp: Reject negative power cap writes in hwmon\n\nhsmp_hwmon_write() takes the user-supplied hwmon value as a signed long\nand assigns \"val / MICROWATT_PER_MILLIWATT\" to msg.args[0], which is a\n__u32.  MICROWATT_PER_MILLIWATT is an unsigned long, so a negative write\nto power1_cap (e.g. \"echo -1 \u003e power1_cap\") is first converted to a huge\nunsigned value by the division and then stored into the u32 argument.\n\nAs a result a nonsensical, multi-gigawatt socket power limit is sent to\nthe SMU via HSMP_SET_SOCKET_POWER_LIMIT instead of the write being\nrejected.\n\nReject negative values with -EINVAL before the conversion.\n\nTested with HSMP enabled:\n\n  CAP=$(dirname $(grep -l amd_hsmp_hwmon \\\n        /sys/class/hwmon/hwmon*/name | head -1))/power1_cap\n\n  # negative write\n  echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  # valid positive write must still work\n  echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n\nBefore:\n  # echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0                             \u003c- accepted; bogus limit sent to SMU\n  # echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0\n\nAfter:\n  # echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  bash: echo: write error: Invalid argument\n  ret=1                             \u003c- rejected with -EINVAL\n  # echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0                             \u003c- valid write still works"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:58:34.349Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2c09cadec116eba3fdbcb5d8d8641f6777d4a11f"
        },
        {
          "url": "https://git.kernel.org/stable/c/1b0a3d915320f1600e5ff43f8bc21b73118480b8"
        },
        {
          "url": "https://git.kernel.org/stable/c/3921bb8635ff2836622df1cdf3194d4f3c1835a4"
        }
      ],
      "title": "platform/x86/amd/hsmp: Reject negative power cap writes in hwmon",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90136",
    "datePublished": "2026-09-17T16:06:35.190Z",
    "dateReserved": "2026-09-11T19:38:34.788Z",
    "dateUpdated": "2026-10-19T08:58:34.349Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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