{"id":"CVE-2026-90136","published":"2026-09-17T17:17:06.173","lastModified":"2026-09-17T17:17:06.173","description":"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 > 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 > $CAP ; echo \"ret=$?\"\n  # valid positive write must still work\n  echo 400000000 > $CAP ; echo \"ret=$?\"\n\nBefore:\n  # echo -1000000 > $CAP ; echo \"ret=$?\"\n  ret=0                             <- accepted; bogus limit sent to SMU\n  # echo 400000000 > $CAP ; echo \"ret=$?\"\n  ret=0\n\nAfter:\n  # echo -1000000 > $CAP ; echo \"ret=$?\"\n  bash: echo: write error: Invalid argument\n  ret=1                             <- rejected with -EINVAL\n  # echo 400000000 > $CAP ; echo \"ret=$?\"\n  ret=0                             <- valid write still works","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/1b0a3d915320f1600e5ff43f8bc21b73118480b8","tags":[]},{"url":"https://git.kernel.org/stable/c/2c09cadec116eba3fdbcb5d8d8641f6777d4a11f","tags":[]},{"url":"https://git.kernel.org/stable/c/3921bb8635ff2836622df1cdf3194d4f3c1835a4","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}