{"id":"CVE-2026-90136","summary":"platform/x86/amd/hsmp: Reject negative power cap writes in hwmon","details":"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","modified":"2026-09-18T03:48:35.483983785Z","published":"2026-09-17T16:06:35.190Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90136.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1b0a3d915320f1600e5ff43f8bc21b73118480b8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2c09cadec116eba3fdbcb5d8d8641f6777d4a11f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3921bb8635ff2836622df1cdf3194d4f3c1835a4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90136.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90136"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"92c025db52bb94a032eb3d473bb81e62c19ddbd3"},{"fixed":"2c09cadec116eba3fdbcb5d8d8641f6777d4a11f"},{"fixed":"1b0a3d915320f1600e5ff43f8bc21b73118480b8"},{"fixed":"3921bb8635ff2836622df1cdf3194d4f3c1835a4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90136.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.16.0"},{"fixed":"6.18.52"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90136.json"}}],"schema_version":"1.9.0"}