linux-kernel - [PATCH 12/18] Thermal/int340x: prevent bounds-check bypass via speculative execution

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Date:   Fri, 05 Jan 2018 17:10:59 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org, gregkh@...uxfoundation.org,
        peterz@...radead.org, netdev@...r.kernel.org,
        Eduardo Valentin <edubezval@...il.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Zhang Rui <rui.zhang@...el.com>, torvalds@...ux-foundation.org,
        tglx@...utronix.de, Elena Reshetova <elena.reshetova@...el.com>,
        alan@...ux.intel.com
Subject: [PATCH 12/18] Thermal/int340x: prevent bounds-check bypass via
 speculative execution

Static analysis reports that 'trip' may be a user controlled value that
is used as a data dependency to read '*temp' from the 'd->aux_trips'
array.  In order to avoid potential leaks of kernel memory values, block
speculative execution of the instruction stream that could issue reads
based on an invalid value of '*temp'.

Based on an original patch by Elena Reshetova.

Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: Zhang Rui <rui.zhang@...el.com>
Cc: Eduardo Valentin <edubezval@...il.com>
Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 .../thermal/int340x_thermal/int340x_thermal_zone.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/thermal/int340x_thermal/int340x_thermal_zone.c b/drivers/thermal/int340x_thermal/int340x_thermal_zone.c
index 145a5c53ff5c..442a1d9bf7ad 100644
--- a/drivers/thermal/int340x_thermal/int340x_thermal_zone.c
+++ b/drivers/thermal/int340x_thermal/int340x_thermal_zone.c
@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/acpi.h>
 #include <linux/thermal.h>
+#include <linux/compiler.h>
 #include "int340x_thermal_zone.h"
 
 static int int340x_thermal_get_zone_temp(struct thermal_zone_device *zone,
@@ -52,20 +53,21 @@ static int int340x_thermal_get_trip_temp(struct thermal_zone_device *zone,
 					 int trip, int *temp)
 {
 	struct int34x_thermal_zone *d = zone->devdata;
+	unsigned long *elem;
 	int i;
 
 	if (d->override_ops && d->override_ops->get_trip_temp)
 		return d->override_ops->get_trip_temp(zone, trip, temp);
 
-	if (trip < d->aux_trip_nr)
-		*temp = d->aux_trips[trip];
-	else if (trip == d->crt_trip_id)
+	if ((elem = nospec_array_ptr(d->aux_trips, trip, d->aux_trip_nr))) {
+		*temp = *elem;
+	} else if (trip == d->crt_trip_id) {
 		*temp = d->crt_temp;
-	else if (trip == d->psv_trip_id)
+	} else if (trip == d->psv_trip_id) {
 		*temp = d->psv_temp;
-	else if (trip == d->hot_trip_id)
+	} else if (trip == d->hot_trip_id) {
 		*temp = d->hot_temp;
-	else {
+	} else {
 		for (i = 0; i < INT340X_THERMAL_MAX_ACT_TRIP_COUNT; i++) {
 			if (d->act_trips[i].valid &&
 			    d->act_trips[i].id == trip) {