3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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From: "Gustavo A. R. Silva" gustavo@embeddedor.com
commit d49dbfade96d5b0863ca8a90122a805edd5ef50a upstream.
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
Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com Signed-off-by: Guenter Roeck linux@roeck-us.net [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/hwmon/nct6775.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/hwmon/nct6775.c +++ b/drivers/hwmon/nct6775.c @@ -57,6 +57,7 @@ #include <linux/mutex.h> #include <linux/acpi.h> #include <linux/io.h> +#include <linux/nospec.h> #include "lm75.h"
#define USE_ALTERNATE @@ -2438,6 +2439,7 @@ store_pwm_weight_temp_sel(struct device return err; if (val > NUM_TEMP) return -EINVAL; + val = array_index_nospec(val, NUM_TEMP + 1); if (val && (!(data->have_temp & (1 << (val - 1))) || !data->temp_src[val - 1])) return -EINVAL;