[PATCH 2/2] nvmet: fix a race condition between release_queue and io_work

[Maurizio Lombardi <mlombard@redhat.com>]

If the initiator executes a reset controller operation while
performing I/O, the target kernel will crash because of a race condition
between release_queue and io_work;
nvmet_tcp_uninit_data_in_cmds() may be executed while io_work
is running, calling flush_work(io_work) was not sufficient to
prevent this because io_work could requeue itself.

* Fix this bug by preventing io_work from being enqueued when
sk_user_data is NULL (it means that the queue is going to be deleted)

* Ensure that all the memory allocated for the commands' iovec is freed

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
---
 drivers/nvme/target/tcp.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 2f03a94725ae..1eedbd83c95f 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -551,6 +551,7 @@ static void nvmet_tcp_queue_response(struct nvmet_req *req)
 	struct nvmet_tcp_cmd *cmd =
 		container_of(req, struct nvmet_tcp_cmd, req);
 	struct nvmet_tcp_queue	*queue = cmd->queue;
+	struct socket *sock = queue->sock;
 	struct nvme_sgl_desc *sgl;
 	u32 len;
 
@@ -570,7 +571,10 @@ static void nvmet_tcp_queue_response(struct nvmet_req *req)
 	}
 
 	llist_add(&cmd->lentry, &queue->resp_list);
-	queue_work_on(queue_cpu(queue), nvmet_tcp_wq, &cmd->queue->io_work);
+	read_lock_bh(&sock->sk->sk_callback_lock);
+	if (likely(sock->sk->sk_user_data))
+		queue_work_on(queue_cpu(queue), nvmet_tcp_wq, &cmd->queue->io_work);
+	read_unlock_bh(&sock->sk->sk_callback_lock);
 }
 
 static void nvmet_tcp_execute_request(struct nvmet_tcp_cmd *cmd)
@@ -1427,7 +1431,9 @@ static void nvmet_tcp_uninit_data_in_cmds(struct nvmet_tcp_queue *queue)
 
 	for (i = 0; i < queue->nr_cmds; i++, cmd++) {
 		if (nvmet_tcp_need_data_in(cmd))
-			nvmet_tcp_finish_cmd(cmd);
+			nvmet_req_uninit(&cmd->req);
+		nvmet_tcp_unmap_pdu_iovec(cmd);
+		nvmet_tcp_free_iovec(cmd);
 	}
 
 	if (!queue->nr_cmds && nvmet_tcp_need_data_in(&queue->connect)) {
@@ -1447,11 +1453,10 @@ static void nvmet_tcp_release_queue_work(struct work_struct *w)
 	mutex_unlock(&nvmet_tcp_queue_mutex);
 
 	nvmet_tcp_restore_socket_callbacks(queue);
-	flush_work(&queue->io_work);
+	cancel_work_sync(&queue->io_work);
 
 	nvmet_tcp_uninit_data_in_cmds(queue);
 	nvmet_sq_destroy(&queue->nvme_sq);
-	cancel_work_sync(&queue->io_work);
 	sock_release(queue->sock);
 	nvmet_tcp_free_cmds(queue);
 	if (queue->hdr_digest || queue->data_digest)
-- 
2.27.0