can: bcm: fix infoleak in struct bcm_msg_head

On 64-bit systems, struct bcm_msg_head has an added padding of 4 bytes between
struct members count and ival1. Even though all struct members are initialized,
the 4-byte hole will contain data from the kernel stack. This patch zeroes out
struct bcm_msg_head before usage, preventing infoleaks to userspace.

Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol")
Link: https://lore.kernel.org/r/trinity-7c1b2e82-e34f-4885-8060-2cd7a13769ce-1623532166177@3c-app-gmx-bs52
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Norbert Slusarek <nslusarek@gmx.net>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/net/can/bcm.c b/net/can/bcm.c
index f00176b..f3e4d95 100644 (file)
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -406,6 +406,7 @@ static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
                if (!op->count && (op->flags & TX_COUNTEVT)) {
 
                        /* create notification to user */
+                       memset(&msg_head, 0, sizeof(msg_head));
                        msg_head.opcode  = TX_EXPIRED;
                        msg_head.flags   = op->flags;
                        msg_head.count   = op->count;
@@ -443,6 +444,7 @@ static void bcm_rx_changed(struct bcm_op *op, struct canfd_frame *data)
        /* this element is not throttled anymore */
        data->flags &= (BCM_CAN_FLAGS_MASK|RX_RECV);
 
+       memset(&head, 0, sizeof(head));
        head.opcode  = RX_CHANGED;
        head.flags   = op->flags;
        head.count   = op->count;
@@ -564,6 +566,7 @@ static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
        }
 
        /* create notification to user */
+       memset(&msg_head, 0, sizeof(msg_head));
        msg_head.opcode  = RX_TIMEOUT;
        msg_head.flags   = op->flags;
        msg_head.count   = op->count;