On 12.06.21 23:09, Norbert Slusarek wrote:
From: Norbert Slusarek <nslusarek@xxxxxxx>
Date: Sat, 12 Jun 2021 22:18:54 +0200
Subject: [PATCH] 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")
Signed-off-by: Norbert Slusarek <nslusarek@xxxxxxx>
Acked-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
Thanks Norbert!
Yes, when this data structure was created in 2003 either 64 bit machines
were far away for me and infoleaks were not a hot topic like today.
Would be interesting to check where data structures are used in the
Linux UAPI that became an infoleak in the 32-to-64-bit compilation
transistion.
Thanks for the heads up!
Best regards,
Oliver
---
net/can/bcm.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 909b9e684e04..b03062f84fe7 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -402,6 +402,7 @@ 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;
@@ -439,6 +440,7 @@ 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;
@@ -560,6 +562,7 @@ 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;
--
2.30.2
