can: bcm: fix infoleak in struct bcm_msg_head

commit 5e87ddbe3942e27e939bdc02deb8579b0cbd8ecc upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/can/bcm.c b/net/can/bcm.c
index 1f15622d3c657158a179d19622594d6ce3d27660..bd9e10db6cd7a5f26f170aea8317bf113e7bbf28 100644 (file)
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -392,6 +392,7 @@ static void bcm_tx_timeout_tsklet(unsigned long data)
                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;
@@ -439,6 +440,7 @@ static void bcm_rx_changed(struct bcm_op *op, struct can_frame *data)
        /* this element is not throttled anymore */
        data->can_dlc &= (BCM_CAN_DLC_MASK|RX_RECV);
 
+       memset(&head, 0, sizeof(head));
        head.opcode  = RX_CHANGED;
        head.flags   = op->flags;
        head.count   = op->count;
@@ -550,6 +552,7 @@ static void bcm_rx_timeout_tsklet(unsigned long data)
        struct bcm_msg_head msg_head;
 
        /* 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;