net/mlx5: IPSec, Fix a race between concurrent sandbox QP commands

Sandbox QP Commands are retired in the order they are sent. Outstanding
commands are stored in a linked-list in the order they appear. Once a
response is received and the callback gets called, we pull the first
element off the pending list, assuming they correspond.

Sending a message and adding it to the pending list is not done atomically,
hence there is an opportunity for a race between concurrent requests.

Bind both send and add under a critical section.

Fixes: bebb23e6cb02 ("net/mlx5: Accel, Add IPSec acceleration interface")
Signed-off-by: Yossi Kuperman <yossiku@mellanox.com>
Signed-off-by: Adi Nissim <adin@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c

@@ -237,19 +237,17 @@ static void *mlx5_fpga_ipsec_cmd_exec(struct mlx5_core_dev *mdev,
 	context->buf.sg[0].data = &context->command;
 
 	spin_lock_irqsave(&fdev->ipsec->pending_cmds_lock, flags);
-	list_add_tail(&context->list, &fdev->ipsec->pending_cmds);
+	res = mlx5_fpga_sbu_conn_sendmsg(fdev->ipsec->conn, &context->buf);
+	if (!res)
+		list_add_tail(&context->list, &fdev->ipsec->pending_cmds);
 	spin_unlock_irqrestore(&fdev->ipsec->pending_cmds_lock, flags);
 
-	res = mlx5_fpga_sbu_conn_sendmsg(fdev->ipsec->conn, &context->buf);
 	if (res) {
-		mlx5_fpga_warn(fdev, "Failure sending IPSec command: %d\n",
-			       res);
-		spin_lock_irqsave(&fdev->ipsec->pending_cmds_lock, flags);
-		list_del(&context->list);
-		spin_unlock_irqrestore(&fdev->ipsec->pending_cmds_lock, flags);
+		mlx5_fpga_warn(fdev, "Failed to send IPSec command: %d\n", res);
 		kfree(context);
 		return ERR_PTR(res);
 	}
+
 	/* Context will be freed by wait func after completion */
 	return context;
 }