[PATCH 4.14 43/88] can: bcm: fix infoleak in struct bcm_msg_head

Sasha Levin
2021-06-28T15:09:20Z

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 12d851c4604d..f691afcc5b8b 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -406,6 +406,7 @@ 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;
@@ -453,6 +454,7 @@ 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;
@@ -567,6 +569,7 @@ 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