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Sashiko AI review found 1 potential issue(s) to consider: > - [Medium] sysfs: returning 0 on error in store callback causes userspace infinite loop > -- > > commit fdbe8069cbe324980fc35768d7993da6a046117b > Author: Karthik Poosa > drm/xe/hwmon: Handle pcode read failures of xe_hwmon_pcode_rmw_power_limit > > This commit adds error handling for pcode read failures in > xe_hwmon_pcode_rmw_power_limit() and checks the returned error in callers > to prevent updating power limit settings with invalid data. > >> diff --git a/drivers/gpu/drm/xe/xe_hwmon.c b/drivers/gpu/drm/xe/xe_hwmon.c >> --- a/drivers/gpu/drm/xe/xe_hwmon.c >> +++ b/drivers/gpu/drm/xe/xe_hwmon.c > [ ... ] >> @@ -679,11 +683,13 @@ xe_hwmon_power_max_interval_store(struct device *dev, struct device_attribute *a >> >> mutex_lock(&hwmon->hwmon_lock); >> >> - if (hwmon->xe->info.has_mbx_power_limits) >> - xe_hwmon_pcode_rmw_power_limit(hwmon, power_attr, channel, PWR_LIM_TIME, rxy); >> - else >> + if (hwmon->xe->info.has_mbx_power_limits) { >> + if (xe_hwmon_pcode_rmw_power_limit(hwmon, power_attr, channel, PWR_LIM_TIME, rxy)) >> + count = 0; > [Severity: Medium] > In xe_hwmon_power_max_interval_store() within drivers/gpu/drm/xe/xe_hwmon.c, > will setting count to 0 here cause userspace tools to enter an infinite loop? > > When a sysfs store callback returns 0 instead of a negative error code, it > indicates to the virtual file system that 0 bytes were written and swallows > the error. Standard userspace utilities (like echo or dd) often treat a > 0-byte write as a short write and retry infinitely. > > If an administrative user or script writes to the sysfs attribute and the > underlying pcode mailbox operation fails, could this cause an infinite loop > that consumes maximum processor time while simultaneously flooding the kernel > log with error messages? > > Should this return the negative error code from > xe_hwmon_pcode_rmw_power_limit() instead of setting count to 0? I shall return -EIO instead of 0 here in next revision. > >> + } else { >> r = xe_mmio_rmw32(mmio, xe_hwmon_get_reg(hwmon, REG_PKG_RAPL_LIMIT, channel), >> PWR_LIM_TIME, rxy); >> + } >> >> mutex_unlock(&hwmon->hwmon_lock);