powercap: restrict energy meter to root access

commit 949dd0104c496fa7c14991a23c03c62e44637e71 upstream.

Remove non-privileged user access to power data contained in
/sys/class/powercap/intel-rapl*/*/energy_uj

Non-privileged users currently have read access to power data and can
use this data to form a security attack. Some privileged
drivers/applications need read access to this data, but don't expose it
to non-privileged users.

For example, thermald uses this data to ensure that power management
works correctly. Thus removing non-privileged access is preferred over
completely disabling this power reporting capability with
CONFIG_INTEL_RAPL=n.

Fixes: 95677a9 ("PowerCap: Fix mode for energy counter")
Signed-off-by: Len Brown <[email protected]>
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/powercap/powercap_sys.c

@@ -379,9 +379,9 @@ static void create_power_zone_common_attributes(
 					&dev_attr_max_energy_range_uj.attr;
 	if (power_zone->ops->get_energy_uj) {
 		if (power_zone->ops->reset_energy_uj)
-			dev_attr_energy_uj.attr.mode = S_IWUSR | S_IRUGO;
+			dev_attr_energy_uj.attr.mode = S_IWUSR | S_IRUSR;
 		else
-			dev_attr_energy_uj.attr.mode = S_IRUGO;
+			dev_attr_energy_uj.attr.mode = S_IRUSR;
 		power_zone->zone_dev_attrs[count++] =
 					&dev_attr_energy_uj.attr;
 	}