[PATCH 4.9 38/71] can: bcm: fix infoleak in struct bcm_msg_head

[Sasha Levin <sashal@kernel.org>]

From: Norbert Slusarek <nslusarek@gmx.net>

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>
---
 net/can/bcm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/can/bcm.c b/net/can/bcm.c
index c99e7c75eeee..077606585ed9 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -405,6 +405,7 @@ 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;
@@ -452,6 +453,7 @@ 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;
@@ -566,6 +568,7 @@ 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;
-- 
2.30.2