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Date: Wed, 5 Apr 2023 11:24:44 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org, linux-can@...r.kernel.org,
kernel@...gutronix.de, Oliver Hartkopp <socketcan@...tkopp.net>,
"Dae R . Jeong" <threeearcat@...il.com>,
Hillf Danton <hdanton@...a.com>, stable@...r.kernel.org,
Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net 4/4] can: isotp: fix race between isotp_sendsmg() and isotp_release()
From: Oliver Hartkopp <socketcan@...tkopp.net>
As discussed with Dae R. Jeong and Hillf Danton here [1] the sendmsg()
function in isotp.c might get into a race condition when restoring the
former tx.state from the old_state.
Remove the old_state concept and implement proper locking for the
ISOTP_IDLE transitions in isotp_sendmsg(), inspired by a
simplification idea from Hillf Danton.
Introduce a new tx.state ISOTP_SHUTDOWN and use the same locking
mechanism from isotp_release() which resolves a potential race between
isotp_sendsmg() and isotp_release().
[1] https://lore.kernel.org/linux-can/ZB%2F93xJxq%2FBUqAgG@dragonet
v1: https://lore.kernel.org/all/20230331102114.15164-1-socketcan@hartkopp.net
v2: https://lore.kernel.org/all/20230331123600.3550-1-socketcan@hartkopp.net
take care of signal interrupts for wait_event_interruptible() in
isotp_release()
v3: https://lore.kernel.org/all/20230331130654.9886-1-socketcan@hartkopp.net
take care of signal interrupts for wait_event_interruptible() in
isotp_sendmsg() in the wait_tx_done case
v4: https://lore.kernel.org/all/20230331131935.21465-1-socketcan@hartkopp.net
take care of signal interrupts for wait_event_interruptible() in
isotp_sendmsg() in ALL cases
Cc: Dae R. Jeong <threeearcat@...il.com>
Cc: Hillf Danton <hdanton@...a.com>
Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
Fixes: 4f027cba8216 ("can: isotp: split tx timer into transmission and timeout")
Link: https://lore.kernel.org/all/20230331131935.21465-1-socketcan@hartkopp.net
Cc: stable@...r.kernel.org
[mkl: rephrase commit message]
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
net/can/isotp.c | 55 ++++++++++++++++++++++++++++---------------------
1 file changed, 31 insertions(+), 24 deletions(-)
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 281b7766c54e..5761d4ab839d 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -119,7 +119,8 @@ enum {
ISOTP_WAIT_FIRST_FC,
ISOTP_WAIT_FC,
ISOTP_WAIT_DATA,
- ISOTP_SENDING
+ ISOTP_SENDING,
+ ISOTP_SHUTDOWN,
};
struct tpcon {
@@ -880,8 +881,8 @@ static enum hrtimer_restart isotp_tx_timer_handler(struct hrtimer *hrtimer)
txtimer);
struct sock *sk = &so->sk;
- /* don't handle timeouts in IDLE state */
- if (so->tx.state == ISOTP_IDLE)
+ /* don't handle timeouts in IDLE or SHUTDOWN state */
+ if (so->tx.state == ISOTP_IDLE || so->tx.state == ISOTP_SHUTDOWN)
return HRTIMER_NORESTART;
/* we did not get any flow control or echo frame in time */
@@ -918,7 +919,6 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
struct sock *sk = sock->sk;
struct isotp_sock *so = isotp_sk(sk);
- u32 old_state = so->tx.state;
struct sk_buff *skb;
struct net_device *dev;
struct canfd_frame *cf;
@@ -928,23 +928,24 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
int off;
int err;
- if (!so->bound)
+ if (!so->bound || so->tx.state == ISOTP_SHUTDOWN)
return -EADDRNOTAVAIL;
+wait_free_buffer:
/* we do not support multiple buffers - for now */
- if (cmpxchg(&so->tx.state, ISOTP_IDLE, ISOTP_SENDING) != ISOTP_IDLE ||
- wq_has_sleeper(&so->wait)) {
- if (msg->msg_flags & MSG_DONTWAIT) {
- err = -EAGAIN;
- goto err_out;
- }
+ if (wq_has_sleeper(&so->wait) && (msg->msg_flags & MSG_DONTWAIT))
+ return -EAGAIN;
- /* wait for complete transmission of current pdu */
- err = wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
- if (err)
- goto err_out;
+ /* wait for complete transmission of current pdu */
+ err = wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
+ if (err)
+ goto err_event_drop;
- so->tx.state = ISOTP_SENDING;
+ if (cmpxchg(&so->tx.state, ISOTP_IDLE, ISOTP_SENDING) != ISOTP_IDLE) {
+ if (so->tx.state == ISOTP_SHUTDOWN)
+ return -EADDRNOTAVAIL;
+
+ goto wait_free_buffer;
}
if (!size || size > MAX_MSG_LENGTH) {
@@ -1074,7 +1075,9 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
if (wait_tx_done) {
/* wait for complete transmission of current pdu */
- wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
+ err = wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
+ if (err)
+ goto err_event_drop;
if (sk->sk_err)
return -sk->sk_err;
@@ -1082,13 +1085,15 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
return size;
+err_event_drop:
+ /* got signal: force tx state machine to be idle */
+ so->tx.state = ISOTP_IDLE;
+ hrtimer_cancel(&so->txfrtimer);
+ hrtimer_cancel(&so->txtimer);
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)
- wake_up_interruptible(&so->wait);
+ so->tx.state = ISOTP_IDLE;
+ wake_up_interruptible(&so->wait);
return err;
}
@@ -1150,10 +1155,12 @@ static int isotp_release(struct socket *sock)
net = sock_net(sk);
/* wait for complete transmission of current pdu */
- wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
+ while (wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE) == 0 &&
+ cmpxchg(&so->tx.state, ISOTP_IDLE, ISOTP_SHUTDOWN) != ISOTP_IDLE)
+ ;
/* force state machines to be idle also when a signal occurred */
- so->tx.state = ISOTP_IDLE;
+ so->tx.state = ISOTP_SHUTDOWN;
so->rx.state = ISOTP_IDLE;
spin_lock(&isotp_notifier_lock);
--
2.39.2
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