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 [email protected]

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 drivers/hwmon/nct6775.c | 2 ++
 1 file changed, 2 insertions(+)

drivers/hwmon/nct6775.c +2 -0

index c6bd61e..944f5b6 100644
@@ -63,6 +63,7 @@
 #include <linux/bitops.h>
 #include <linux/dmi.h>
 #include <linux/io.h>
+#include <linux/nospec.h>
 #include "lm75.h"
 
 #define USE_ALTERNATE

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

Signature · 1 line

2.7.4