net/mlx5: fix hairpin Tx queue creation error path

net/mlx5: fix hairpin Tx queue creation error path

The mlx5_txq_obj_hairpin_new function defines a pointer named tmpl and
allocates memory for it using the rte_zmalloc_socket function.
Later, this function allocates memory to a variable inside tmpl using
the mlx5_devx_cmd_create_sq function.

In both cases, if the allocation fails, the code jumps to the error
label and frees allocated resources. However, in the first jump there
are still no resources to free and the jump only for the line return
NULL is unnecessary. Even worse, when it jumps to error label with
invalid tmpl it actually does dereference to a null pointer.
In contrast, the second jump needs to free the tmpl variable but the
function instead of freeing, tries to free the variable that it just
failed to allocate, and another variable that has never been allocated.
In addition, for another error, the function returns NULL without
freeing the tmpl variable before, causing a memory leak.

Delete the error label and replace each jump with local return NULL and
free tmpl variable if needed.

Fixes: ae18a1ae9692 ("net/mlx5: support Tx hairpin queues")
Cc: stable@dpdk.org
Signed-off-by: Michael Baum <michaelba@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>