[PATCH AUTOSEL 6.1 28/53] hwmon: (pc87360) Bounds check data->innr usage

Sasha Levin
2024-01-22T15:11:01Z

From: Kees Cook <keescook@chromium.org>

[ Upstream commit 4265eb062a7303e537ab3792ade31f424c3c5189 ]

Without visibility into the initializers for data->innr, GCC suspects
using it as an index could walk off the end of the various 14-element
arrays in data. Perform an explicit clamp to the array size. Silences
the following warning with GCC 12+:

../drivers/hwmon/pc87360.c: In function 'pc87360_update_device':
../drivers/hwmon/pc87360.c:341:49: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
341 | data->in_max[i] = pc87360_read_value(data,
| ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
342 | LD_IN, i,
| ~~~~~~~~~
343 | PC87365_REG_IN_MAX);
| ~~~~~~~~~~~~~~~~~~~
../drivers/hwmon/pc87360.c:209:12: note: at offset 255 into destination object 'in_max' of size 14
209 | u8 in_max[14]; /* Register value */
| ^~~~~~

Cc: Jim Cromie <jim.cromie@gmail.com>
Cc: Jean Delvare <jdelvare@suse.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: linux-hwmon@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20231130200207.work.679-kees@kernel.org
[groeck: Added comment into code clarifying context]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/hwmon/pc87360.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/pc87360.c b/drivers/hwmon/pc87360.c
index a4adc8bd531f..534a6072036c 100644
--- a/drivers/hwmon/pc87360.c
+++ b/drivers/hwmon/pc87360.c
@@ -323,7 +323,11 @@ static struct pc87360_data *pc87360_update_device(struct device *dev)
}

/* Voltages */
- for (i = 0; i < data->innr; i++) {
+ /*
+ * The min() below does not have any practical meaning and is
+ * only needed to silence a warning observed with gcc 12+.
+ */
+ for (i = 0; i < min(data->innr, ARRAY_SIZE(data->in)); i++) {
data->in_status[i] = pc87360_read_value(data, LD_IN, i,
PC87365_REG_IN_STATUS);
/* Clear bits */
--
2.43.0