platform/x86/amd/hsmp: Reject negative power cap writes in hwmon

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Summary

CVECVE-2026-90136
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 17:17:06 UTC
Updated2026-09-17 17:17:06 UTC
DescriptionIn 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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 92c025db52bb94a032eb3d473bb81e62c19ddbd3 2c09cadec116eba3fdbcb5d8d8641f6777d4a11f git Not specified
CNA Linux Linux affected 92c025db52bb94a032eb3d473bb81e62c19ddbd3 1b0a3d915320f1600e5ff43f8bc21b73118480b8 git Not specified
CNA Linux Linux affected 92c025db52bb94a032eb3d473bb81e62c19ddbd3 3921bb8635ff2836622df1cdf3194d4f3c1835a4 git Not specified
CNA Linux Linux affected 6.16 Not specified
CNA Linux Linux unaffected 6.16 semver Not specified
CNA Linux Linux unaffected 6.18.52 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/1b0a3d915320f1600e5ff43f8bc21b73118480b8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3921bb8635ff2836622df1cdf3194d4f3c1835a4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2c09cadec116eba3fdbcb5d8d8641f6777d4a11f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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