hwmon: (nct6775) Fix potential Spectre v1

val can be indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: vers/hwmon/nct6775.c:2698 store_pwm_weight_temp_sel() warn: potential spectre issue 'data->temp_src' [r] Fix this by sanitizing val before using it to index data->temp_src Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2

Gustavo A. R. Silva committed 8 years ago

Commit d49dbfa1 parent f196dec1 file · +2 −0Browse files

Unified · Split

drivers/hwmon/nct6775.c+2−0

@@ -63,6 +63,7 @@ · 62 unmodified lines
63	63	#include <linux/bitops.h>
64	64	#include <linux/dmi.h>
65	65	#include <linux/io.h>
	66	+#include <linux/nospec.h>
66	67	#include "lm75.h"
67	68
68	69	#define USE_ALTERNATE
@@ -2689,6 +2690,7 @@ store_pwm_weight_temp_sel(struct device dev, struct device_attribute attr, · 2620 unmodified lines
2689	2690	return err;
2690	2691	if (val > NUM_TEMP)
2691	2692	return -EINVAL;
	2693	+ val = array_index_nospec(val, NUM_TEMP + 1);
2692	2694	if (val && (!(data->have_temp & BIT(val - 1)) \|\|
2693	2695	!data->temp_src[val - 1]))
2694	2696	return -EINVAL;