net: mlx5: Add a missing check on idr_find, free buf

idr_find() can return a NULL value to 'flow' which is used without a
check. The patch adds a check to avoid potential NULL pointer dereference.

In case of mlx5_fpga_sbu_conn_sendmsg() failure, free buf allocated
using kzalloc.

Fixes: ab412e1d ("net/mlx5: Accel, add TLS rx offload routines")
Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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

@@ -217,15 +217,21 @@ int mlx5_fpga_tls_resync_rx(struct mlx5_core_dev *mdev, u32 handle, u32 seq,
 	void *cmd;
 	int ret;
 
+	rcu_read_lock();
+	flow = idr_find(&mdev->fpga->tls->rx_idr, ntohl(handle));
+	rcu_read_unlock();
+
+	if (!flow) {
+		WARN_ONCE(1, "Received NULL pointer for handle\n");
+		return -EINVAL;
+	}
+
 	buf = kzalloc(size, GFP_ATOMIC);
 	if (!buf)
 		return -ENOMEM;
 
 	cmd = (buf + 1);
 
-	rcu_read_lock();
-	flow = idr_find(&mdev->fpga->tls->rx_idr, ntohl(handle));
-	rcu_read_unlock();
 	mlx5_fpga_tls_flow_to_cmd(flow, cmd);
 
 	MLX5_SET(tls_cmd, cmd, swid, ntohl(handle));
@@ -238,6 +244,8 @@ int mlx5_fpga_tls_resync_rx(struct mlx5_core_dev *mdev, u32 handle, u32 seq,
 	buf->complete = mlx_tls_kfree_complete;
 
 	ret = mlx5_fpga_sbu_conn_sendmsg(mdev->fpga->tls->conn, buf);
+	if (ret < 0)
+		kfree(buf);
 
 	return ret;
 }