{"id":"CVE-2026-90136","state":"PUBLISHED","title":"platform/x86/amd/hsmp: Reject negative power cap writes in hwmon","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","publishedAt":"2026-09-17T16:06:35.190Z","updatedAt":"2026-10-19T08:58:34.349Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"92c025db52bb94a032eb3d473bb81e62c19ddbd3","status":"affected","lessThan":"2c09cadec116eba3fdbcb5d8d8641f6777d4a11f","versionType":"git"},{"version":"92c025db52bb94a032eb3d473bb81e62c19ddbd3","status":"affected","lessThan":"1b0a3d915320f1600e5ff43f8bc21b73118480b8","versionType":"git"},{"version":"92c025db52bb94a032eb3d473bb81e62c19ddbd3","status":"affected","lessThan":"3921bb8635ff2836622df1cdf3194d4f3c1835a4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/platform/x86/amd/hsmp/hwmon.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.16","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/platform/x86/amd/hsmp/hwmon.c"]}],"references":["https://git.kernel.org/stable/c/2c09cadec116eba3fdbcb5d8d8641f6777d4a11f","https://git.kernel.org/stable/c/1b0a3d915320f1600e5ff43f8bc21b73118480b8","https://git.kernel.org/stable/c/3921bb8635ff2836622df1cdf3194d4f3c1835a4"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/90xxx/CVE-2026-90136.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-90136","state":"PUBLISHED","datePublished":"2026-09-17T16:06:35.190Z","dateUpdated":"2026-10-19T08:58:34.349Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.788Z"},"containers":{"cna":{"title":"platform/x86/amd/hsmp: Reject negative power cap writes in hwmon","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 > 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"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"92c025db52bb94a032eb3d473bb81e62c19ddbd3","status":"affected","lessThan":"2c09cadec116eba3fdbcb5d8d8641f6777d4a11f","versionType":"git"},{"version":"92c025db52bb94a032eb3d473bb81e62c19ddbd3","status":"affected","lessThan":"1b0a3d915320f1600e5ff43f8bc21b73118480b8","versionType":"git"},{"version":"92c025db52bb94a032eb3d473bb81e62c19ddbd3","status":"affected","lessThan":"3921bb8635ff2836622df1cdf3194d4f3c1835a4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/platform/x86/amd/hsmp/hwmon.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.16","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/platform/x86/amd/hsmp/hwmon.c"]}],"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"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:58:34.349Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"6.18.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}