[PATCH 1/3] can: isotp: sanitize CAN ID checks in isotp_bind()

From: Oliver Hartkopp <socketcan@hartkopp.net>
To: linux-can@vger.kernel.org
Cc: Oliver Hartkopp <socketcan@hartkopp.net>,
	syzbot+2339c27f5c66c652843e@syzkaller.appspotmail.com
Subject: [PATCH 1/3] can: isotp: sanitize CAN ID checks in isotp_bind()
Date: Wed, 16 Mar 2022 17:42:56 +0100	[thread overview]
Message-ID: <20220316164258.54155-1-socketcan@hartkopp.net> (raw)

Syzbot created an environment that lead to a state machine status that
can not be reached with a compliant CAN ID address configuration.
The provided address information consisted of CAN ID 0x6000001 and 0xC28001
which both boil down to 11 bit CAN IDs 0x001 in sending and receiving.

Sanitize the SFF/EFF CAN ID values before performing the address checks.

Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol")
Reported-by: syzbot+2339c27f5c66c652843e@syzkaller.appspotmail.com
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 net/can/isotp.c | 41 +++++++++++++++++++++--------------------
 1 file changed, 21 insertions(+), 20 deletions(-)

diff --git a/net/can/isotp.c b/net/can/isotp.c
index d4c0b4704987..1662103ce125 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1146,19 +1146,30 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 	struct sock *sk = sock->sk;
 	struct isotp_sock *so = isotp_sk(sk);
 	struct net *net = sock_net(sk);
 	int ifindex;
 	struct net_device *dev;
+	canid_t tx_id, rx_id;
 	int err = 0;
 	int notify_enetdown = 0;
 	int do_rx_reg = 1;
 
 	if (len < ISOTP_MIN_NAMELEN)
 		return -EINVAL;
 
-	if (addr->can_addr.tp.tx_id & (CAN_ERR_FLAG | CAN_RTR_FLAG))
-		return -EADDRNOTAVAIL;
+	/* sanitize tx/rx CAN identifiers */
+	tx_id = addr->can_addr.tp.tx_id;
+	if (tx_id & CAN_EFF_FLAG)
+		tx_id &= (CAN_EFF_FLAG | CAN_EFF_MASK);
+	else
+		tx_id &= CAN_SFF_MASK;
+
+	rx_id = addr->can_addr.tp.rx_id;
+	if (rx_id & CAN_EFF_FLAG)
+		rx_id &= (CAN_EFF_FLAG | CAN_EFF_MASK);
+	else
+		rx_id &= CAN_SFF_MASK;
 
 	if (!addr->can_ifindex)
 		return -ENODEV;
 
 	lock_sock(sk);
@@ -1166,25 +1177,17 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 	/* do not register frame reception for functional addressing */
 	if (so->opt.flags & CAN_ISOTP_SF_BROADCAST)
 		do_rx_reg = 0;
 
 	/* do not validate rx address for functional addressing */
-	if (do_rx_reg) {
-		if (addr->can_addr.tp.rx_id == addr->can_addr.tp.tx_id) {
-			err = -EADDRNOTAVAIL;
-			goto out;
-		}
-
-		if (addr->can_addr.tp.rx_id & (CAN_ERR_FLAG | CAN_RTR_FLAG)) {
-			err = -EADDRNOTAVAIL;
-			goto out;
-		}
+	if (do_rx_reg && rx_id == tx_id) {
+		err = -EADDRNOTAVAIL;
+		goto out;
 	}
 
 	if (so->bound && addr->can_ifindex == so->ifindex &&
-	    addr->can_addr.tp.rx_id == so->rxid &&
-	    addr->can_addr.tp.tx_id == so->txid)
+	    rx_id == so->rxid && tx_id == so->txid)
 		goto out;
 
 	dev = dev_get_by_index(net, addr->can_ifindex);
 	if (!dev) {
 		err = -ENODEV;
@@ -1204,20 +1207,18 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 		notify_enetdown = 1;
 
 	ifindex = dev->ifindex;
 
 	if (do_rx_reg) {
-		can_rx_register(net, dev, addr->can_addr.tp.rx_id,
-				SINGLE_MASK(addr->can_addr.tp.rx_id),
+		can_rx_register(net, dev, rx_id, SINGLE_MASK(rx_id),
 				isotp_rcv, sk, "isotp", sk);
 
 		/* no consecutive frame echo skb in flight */
 		so->cfecho = 0;
 
 		/* register for echo skb's */
-		can_rx_register(net, dev, addr->can_addr.tp.tx_id,
-				SINGLE_MASK(addr->can_addr.tp.tx_id),
+		can_rx_register(net, dev, tx_id, SINGLE_MASK(tx_id),
 				isotp_rcv_echo, sk, "isotpe", sk);
 	}
 
 	dev_put(dev);
 
@@ -1237,12 +1238,12 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 		}
 	}
 
 	/* switch to new settings */
 	so->ifindex = ifindex;
-	so->rxid = addr->can_addr.tp.rx_id;
-	so->txid = addr->can_addr.tp.tx_id;
+	so->rxid = rx_id;
+	so->txid = tx_id;
 	so->bound = 1;
 
 out:
 	release_sock(sk);
 
-- 
2.30.2

