Re: [PATCH] can: bcm: fix infoleak in struct bcm_msg_head
From: Oliver Hartkopp <socketcan@hartkopp.net>
Date: 2021-06-13 09:51:53
Also in:
linux-can
On 12.06.21 23:09, Norbert Slusarek wrote:
From: Norbert Slusarek <redacted>
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 <redacted>Acked-by: Oliver Hartkopp <socketcan@hartkopp.net> 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
quoted hunk ↗ jump to hunk
--- 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