linux-kernel - [PATCH 5.4 50/90] can: bcm: fix infoleak in struct bcm_msg

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Message-Id: <20210621154905.834965762@linuxfoundation.org>
Date:   Mon, 21 Jun 2021 18:15:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Norbert Slusarek <nslusarek@....net>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH 5.4 50/90] can: bcm: fix infoleak in struct bcm_msg_head

From: Norbert Slusarek <nslusarek@....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@...r.kernel.org>
Signed-off-by: Norbert Slusarek <nslusarek@....net>
Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/can/bcm.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -404,6 +404,7 @@ static enum hrtimer_restart bcm_tx_timeo
 		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;
@@ -441,6 +442,7 @@ static void bcm_rx_changed(struct bcm_op
 	/* 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;
@@ -562,6 +564,7 @@ static enum hrtimer_restart bcm_rx_timeo
 	}
 
 	/* 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;