[PATCH] nvmet-tcp: fix race between ICReq handling and queue teardown

[Chaitanya Kulkarni <kch@nvidia.com>]

nvmet_tcp_handle_icreq() updates queue->state after sending an
Initialization Connection Response (ICResp), but it does so without
serializing against target-side queue teardown.

If an NVMe/TCP host sends an Initialization Connection Request
(ICReq) and immediately closes the connection, target-side teardown
may start in softirq context before io_work drains the already
buffered ICReq. In that case, nvmet_tcp_schedule_release_queue()
sets queue->state to NVMET_TCP_Q_DISCONNECTING and drops the queue
reference under state_lock.

If io_work later processes that ICReq, nvmet_tcp_handle_icreq() can
still overwrite the state back to NVMET_TCP_Q_LIVE. That defeats the
DISCONNECTING-state guard in nvmet_tcp_schedule_release_queue() and
allows a later socket state change to re-enter teardown and issue a
second kref_put() on an already released queue.

The ICResp send failure path has the same problem. If teardown has
already moved the queue to DISCONNECTING, a send error can still
overwrite the state with NVMET_TCP_Q_FAILED, again reopening the
window for a second teardown path to drop the queue reference.

Fix this by serializing both post-send state transitions with
state_lock and bailing out if teardown has already started.

Use -ESHUTDOWN as an internal sentinel for that bail-out path rather
than propagating it as a transport error like -ECONNRESET. Keep
nvmet_tcp_socket_error() setting rcv_state to NVMET_TCP_RECV_ERR before
honoring that sentinel so receive-side parsing stays quiesced until the
existing release path completes.

Reported-by: Shivam Kumar <skumar47@syr.edu>
Fixes: c46a6465bac2 ("nvmet-tcp: add NVMe over TCP target driver")
Cc: stable@vger.kernel.org
Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
---

Hi Shivam,

This patch is different than the one I posted.

Posted patch :-


		iov.iov_len = sizeof(*icresp);
		ret = kernel_sendmsg(queue->sock, &msg, &iov, 1, iov.iov_len);
		if (ret < 0) {
	-		queue->state = NVMET_TCP_Q_FAILED;
	+		spin_lock_bh(&queue->state_lock);
	+		if (queue->state != NVMET_TCP_Q_DISCONNECTING)
	+			queue->state = NVMET_TCP_Q_FAILED;
	+		spin_unlock_bh(&queue->state_lock);
			return ret; /* queue removal will cleanup */
		}

This patch :-

		iov.iov_len = sizeof(*icresp);
		ret = kernel_sendmsg(queue->sock, &msg, &iov, 1, iov.iov_len);
		if (ret < 0) {
	+		spin_lock_bh(&queue->state_lock);
	+		if (queue->state == NVMET_TCP_Q_DISCONNECTING) {
	+			spin_unlock_bh(&queue->state_lock);
	+			return -ESHUTDOWN;
	+		}
			queue->state = NVMET_TCP_Q_FAILED;
	+		spin_unlock_bh(&queue->state_lock);
			return ret; /* queue removal will cleanup */
		}

It will be great if you can provide tested-by tag on this patch
so we can merge this fix as well.

-ck

---
 drivers/nvme/target/tcp.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 69e971b179ae..98b2ce9a70ca 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -407,7 +407,22 @@ static void nvmet_tcp_fatal_error(struct nvmet_tcp_queue *queue)
 
 static void nvmet_tcp_socket_error(struct nvmet_tcp_queue *queue, int status)
 {
+	/*
+	 * Keep rcv_state at RECV_ERR even for the internal -ESHUTDOWN path.
+	 * nvmet_tcp_handle_icreq() can return -ESHUTDOWN after the ICReq has
+	 * already been consumed and queue teardown has started.
+	 *
+	 * If nvmet_tcp_data_ready() or nvmet_tcp_write_space() queues
+	 * nvmet_tcp_io_work() again before nvmet_tcp_release_queue_work()
+	 * cancels it, the queue must not keep that old receive state.
+	 * Otherwise the next nvmet_tcp_io_work() run can reach
+	 * nvmet_tcp_done_recv_pdu() and try to handle the same ICReq again.
+	 *
+	 * That is why queue->rcv_state needs to be updated before we return.
+	 */
 	queue->rcv_state = NVMET_TCP_RECV_ERR;
+	if (status == -ESHUTDOWN)
+		return;
 	if (status == -EPIPE || status == -ECONNRESET)
 		kernel_sock_shutdown(queue->sock, SHUT_RDWR);
 	else
@@ -922,11 +937,24 @@ static int nvmet_tcp_handle_icreq(struct nvmet_tcp_queue *queue)
 	iov.iov_len = sizeof(*icresp);
 	ret = kernel_sendmsg(queue->sock, &msg, &iov, 1, iov.iov_len);
 	if (ret < 0) {
+		spin_lock_bh(&queue->state_lock);
+		if (queue->state == NVMET_TCP_Q_DISCONNECTING) {
+			spin_unlock_bh(&queue->state_lock);
+			return -ESHUTDOWN;
+		}
 		queue->state = NVMET_TCP_Q_FAILED;
+		spin_unlock_bh(&queue->state_lock);
 		return ret; /* queue removal will cleanup */
 	}
 
+	spin_lock_bh(&queue->state_lock);
+	if (queue->state == NVMET_TCP_Q_DISCONNECTING) {
+		spin_unlock_bh(&queue->state_lock);
+		/* Tell nvmet_tcp_socket_error() teardown is already in progress. */
+		return -ESHUTDOWN;
+	}
 	queue->state = NVMET_TCP_Q_LIVE;
+	spin_unlock_bh(&queue->state_lock);
 	nvmet_prepare_receive_pdu(queue);
 	return 0;
 }
-- 
2.39.5