[PATCH 5.16 0125/1017] can: isotp: sanitize CAN ID checks in isotp_bind()

Greg Kroah-Hartman
2022-04-05T09:31:51Z

From: Oliver Hartkopp <socketcan@hartkopp.net>

commit 3ea566422cbde9610c2734980d1286ab681bb40e upstream.

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")
Link: https://lore.kernel.org/all/20220316164258.54155-1-socketcan@hartkopp.net
Reported-by: syzbot+2339c27f5c66c652843e@syzkaller.appspotmail.com
Signed-off-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/isotp.c | 38 ++++++++++++++++++++------------------
1 file changed, 20 insertions(+), 18 deletions(-)

--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1104,6 +1104,7 @@ static int isotp_bind(struct socket *soc
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;
@@ -1111,8 +1112,18 @@ static int isotp_bind(struct socket *soc
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;
@@ -1124,21 +1135,13 @@ static int isotp_bind(struct socket *soc
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);
@@ -1162,8 +1165,7 @@ static int isotp_bind(struct socket *soc
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);

dev_put(dev);
@@ -1183,8 +1185,8 @@ static int isotp_bind(struct socket *soc

/* 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;