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Commit 1009ccdc authored by Guenter Roeck's avatar Guenter Roeck
Browse files

hwmon: (applesmc) Avoid buffer overruns 



gcc 7.1 complains that the driver uses sprintf() and thus does not validate
the length of output buffers.

drivers/hwmon/applesmc.c: In function 'applesmc_show_fan_position':
drivers/hwmon/applesmc.c:82:21: warning:
	'%d' directive writing between 1 and 5 bytes into a region of size 4

Fix the problem by using scnprintf() instead of sprintf() throughout the
driver. Also explicitly limit the number of supported fans to avoid actual
buffer overruns and thus invalid keys.

Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 5771a8c0

drivers/hwmon/applesmc.c

+9 −4
Original line number Diff line number Diff line
@@ -566,6 +566,8 @@ static int applesmc_init_smcreg_try(void) 
	if (ret)

		return ret;

	s->fan_count = tmp[0];

	if (s->fan_count > 10)

		s->fan_count = 10;



	ret = applesmc_get_lower_bound(&s->temp_begin, "T");

	if (ret)
@@ -811,7 +813,8 @@ static ssize_t applesmc_show_fan_speed(struct device *dev, 
	char newkey[5];

	u8 buffer[2];



	sprintf(newkey, fan_speed_fmt[to_option(attr)], to_index(attr));

	scnprintf(newkey, sizeof(newkey), fan_speed_fmt[to_option(attr)],

		  to_index(attr));



	ret = applesmc_read_key(newkey, buffer, 2);

	speed = ((buffer[0] << 8 | buffer[1]) >> 2);
@@ -834,7 +837,8 @@ static ssize_t applesmc_store_fan_speed(struct device *dev, 
	if (kstrtoul(sysfsbuf, 10, &speed) < 0 || speed >= 0x4000)

		return -EINVAL;		/* Bigger than a 14-bit value */



	sprintf(newkey, fan_speed_fmt[to_option(attr)], to_index(attr));

	scnprintf(newkey, sizeof(newkey), fan_speed_fmt[to_option(attr)],

		  to_index(attr));



	buffer[0] = (speed >> 6) & 0xff;

	buffer[1] = (speed << 2) & 0xff;
@@ -903,7 +907,7 @@ static ssize_t applesmc_show_fan_position(struct device *dev, 
	char newkey[5];

	u8 buffer[17];



	sprintf(newkey, FAN_ID_FMT, to_index(attr));

	scnprintf(newkey, sizeof(newkey), FAN_ID_FMT, to_index(attr));



	ret = applesmc_read_key(newkey, buffer, 16);

	buffer[16] = 0;
@@ -1116,7 +1120,8 @@ static int applesmc_create_nodes(struct applesmc_node_group *groups, int num) 
		}

		for (i = 0; i < num; i++) {

			node = &grp->nodes[i];

			sprintf(node->name, grp->format, i + 1);

			scnprintf(node->name, sizeof(node->name), grp->format,

				  i + 1);

			node->sda.index = (grp->option << 16) | (i & 0xffff);

			node->sda.dev_attr.show = grp->show;

			node->sda.dev_attr.store = grp->store;