Commit d49dbfad authored Aug 15, 2018 by Gustavo A. R. Silva Committed by Guenter Roeck Aug 26, 2018

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



Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

parent f196dec6

drivers/hwmon/nct6775.c

+2 −0

Original line number	Original line	Diff line number	Diff line
	@@ -63,6 +63,7 @@
	#include <linux/bitops.h>		#include <linux/bitops.h>
	#include <linux/dmi.h>		#include <linux/dmi.h>
	#include <linux/io.h>		#include <linux/io.h>
			#include <linux/nospec.h>
	#include "lm75.h"		#include "lm75.h"

	#define USE_ALTERNATE		#define USE_ALTERNATE
	@@ -2689,6 +2690,7 @@ store_pwm_weight_temp_sel(struct device dev, struct device_attribute attr,
	return err;		return err;
	if (val > NUM_TEMP)		if (val > NUM_TEMP)
	return -EINVAL;		return -EINVAL;
			val = array_index_nospec(val, NUM_TEMP + 1);
	if (val && (!(data->have_temp & BIT(val - 1)) \|\|		if (val && (!(data->have_temp & BIT(val - 1)) \|\|
	!data->temp_src[val - 1]))		!data->temp_src[val - 1]))
	return -EINVAL;		return -EINVAL;

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