net/mlx5: Devcom, fix error flow in mlx5_devcom_register_device

commit af87194 upstream.

In case devcom allocation is failed, mlx5 is always freeing the priv.
However, this priv might have been allocated by a different thread,
and freeing it might lead to use-after-free bugs.
Fix it by freeing the priv only in case it was allocated by the
running thread.

Fixes: fadd59f ("net/mlx5: Introduce inter-device communication mechanism")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.c

@@ -110,7 +110,8 @@ struct mlx5_devcom *mlx5_devcom_register_device(struct mlx5_core_dev *dev)
 	priv->devs[idx] = dev;
 	devcom = mlx5_devcom_alloc(priv, idx);
 	if (!devcom) {
-		kfree(priv);
+		if (new_priv)
+			kfree(priv);
 		return ERR_PTR(-ENOMEM);
 	}