can: raw: raw_setsockopt: limit number of can_filter that can be set

commit 332b05ca upstream.

This patch adds a check to limit the number of can_filters that can be
set via setsockopt on CAN_RAW sockets. Otherwise allocations > MAX_ORDER
are not prevented resulting in a warning.

Reference: https://lkml.org/lkml/2016/12/2/230Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

include/uapi/linux/can.h

@@ -190,5 +190,6 @@ struct can_filter {
 };
 
 #define CAN_INV_FILTER 0x20000000U /* to be set in can_filter.can_id */
+#define CAN_RAW_FILTER_MAX 512 /* maximum number of can_filter set via setsockopt() */
 
 #endif /* !_UAPI_CAN_H */

net/can/raw.c

@@ -466,6 +466,9 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 		if (optlen % sizeof(struct can_filter) != 0)
 			return -EINVAL;
 
+		if (optlen > CAN_RAW_FILTER_MAX * sizeof(struct can_filter))
+			return -EINVAL;
+
 		count = optlen / sizeof(struct can_filter);
 
 		if (count > 1) {