From 3921bb8635ff2836622df1cdf3194d4f3c1835a4 Mon Sep 17 00:00:00 2001 From: Hemanth Selam Date: Wed, 12 Aug 2026 14:30:12 +0530 Subject: [PATCH] platform/x86/amd/hsmp: Reject negative power cap writes in hwmon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Fixes: 92c025db52bb ("platform/x86/amd/hsmp: Report power via hwmon sensors") Signed-off-by: Hemanth Selam Link: https://patch.msgid.link/20260812090012.140193-1-hemanth.selam@gmail.com Reviewed-by: Ilpo Järvinen Signed-off-by: Ilpo Järvinen --- drivers/platform/x86/amd/hsmp/hwmon.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/platform/x86/amd/hsmp/hwmon.c b/drivers/platform/x86/amd/hsmp/hwmon.c index 0cc9a742497f..c8314eee06f4 100644 --- a/drivers/platform/x86/amd/hsmp/hwmon.c +++ b/drivers/platform/x86/amd/hsmp/hwmon.c @@ -31,6 +31,9 @@ static int hsmp_hwmon_write(struct device *dev, enum hwmon_sensor_types type, if (attr != hwmon_power_cap) return -EOPNOTSUPP; + if (val < 0) + return -EINVAL; + msg.num_args = 1; msg.args[0] = val / MICROWATT_PER_MILLIWATT; msg.msg_id = HSMP_SET_SOCKET_POWER_LIMIT;