can: isotp: fix error path in isotp_sendmsg() to unlock wait queue

commit 8375dfac4f683e1b2c5956d919d36aeedad46699 upstream.

Commit 43a08c3bdac4 ("can: isotp: isotp_sendmsg(): fix TX buffer concurrent
access in isotp_sendmsg()") introduced a new locking scheme that may render
the userspace application in a locking state when an error is detected.
This issue shows up under high load on simultaneously running isotp channels
with identical configuration which is against the ISO specification and
therefore breaks any reasonable PDU communication anyway.

Fixes: 43a08c3bdac4 ("can: isotp: isotp_sendmsg(): fix TX buffer concurrent access in isotp_sendmsg()")
Link: https://lore.kernel.org/all/20220209073601.25728-1-socketcan@hartkopp.net
Cc: stable@vger.kernel.org
Cc: Ziyang Xuan <william.xuanziyang@huawei.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>

diff --git a/net/can/isotp.c b/net/can/isotp.c
index f348fbb2e7dd4bc075a918a742743fa740ec384e..37db4d232313da3cbb53fd7c9ddf0a76782cf74e 100644 (file)
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -885,24 +885,24 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 
        if (!size || size > MAX_MSG_LENGTH) {
                err = -EINVAL;
-               goto err_out;
+               goto err_out_drop;
        }
 
        err = memcpy_from_msg(so->tx.buf, msg, size);
        if (err < 0)
-               goto err_out;
+               goto err_out_drop;
 
        dev = dev_get_by_index(sock_net(sk), so->ifindex);
        if (!dev) {
                err = -ENXIO;
-               goto err_out;
+               goto err_out_drop;
        }
 
        skb = sock_alloc_send_skb(sk, so->ll.mtu + sizeof(struct can_skb_priv),
                                  msg->msg_flags & MSG_DONTWAIT, &err);
        if (!skb) {
                dev_put(dev);
-               goto err_out;
+               goto err_out_drop;
        }
 
        can_skb_reserve(skb);
@@ -967,7 +967,7 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
        if (err) {
                pr_notice_once("can-isotp: %s: can_send_ret %d\n",
                               __func__, err);
-               goto err_out;
+               goto err_out_drop;
        }
 
        if (wait_tx_done) {
@@ -980,6 +980,9 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 
        return size;
 
+err_out_drop:
+       /* drop this PDU and unlock a potential wait queue */
+       old_state = ISOTP_IDLE;
 err_out:
        so->tx.state = old_state;
        if (so->tx.state == ISOTP_IDLE)