Re: [PATCH bpf-next v3 03/14] selftests/bpf: test_xsk: Fix memory leaks

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

On Thu, Sep 04, 2025 at 12:10:18PM +0200, Bastien Curutchet (eBPF Foundation) wrote:
> Some tests introduce memory leaks by not freeing all the pkt_stream
> objects they're creating.
> 
> Fix these memory leaks.

I would appreciate being more explicit here as I've been scratching my
head here.

From what I see the problem is with testapp_stats_rx_dropped() as it's the
one case that uses replace and receive half of pkt streams, both of which
overwrite the default pkt stream. So we lose a pointer to one of pkt
streams and leak it eventually.

Rest of cases should be ok with pkt_stream_restore_default() being called
after each ->test_func() in run_pkt_test().

Anyways let me hear more on your reasoning, thanks! I'm gonna have a
second look tomorrow, I might be missing something.

> 
> Signed-off-by: Bastien Curutchet (eBPF Foundation) <bastien.curutchet@bootlin.com>
> ---
>  tools/testing/selftests/bpf/test_xsk.c | 32 +++++++++++++++++++++++++++++++-
>  1 file changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/test_xsk.c b/tools/testing/selftests/bpf/test_xsk.c
> index 37752b2dad651b36d155051931d7b3b902fac403..e4059c7d0a289449a6b73669fa87f7440b7f55c0 100644
> --- a/tools/testing/selftests/bpf/test_xsk.c
> +++ b/tools/testing/selftests/bpf/test_xsk.c
> @@ -546,6 +546,13 @@ static void pkt_stream_receive_half(struct test_spec *test)
>  	struct pkt_stream *pkt_stream = test->ifobj_tx->xsk->pkt_stream;
>  	u32 i;
>  
> +	if (test->ifobj_rx->xsk->pkt_stream != test->rx_pkt_stream_default)
> +		/* Packet stream has already been replaced so we have to release this one.
> +		 * The newly created one will be freed by the restore_default() at the
> +		 * end of the test
> +		 */
> +		pkt_stream_delete(test->ifobj_rx->xsk->pkt_stream);
> +
>  	test->ifobj_rx->xsk->pkt_stream = pkt_stream_generate(pkt_stream->nb_pkts,
>  							      pkt_stream->pkts[0].len);
>  	pkt_stream = test->ifobj_rx->xsk->pkt_stream;
> @@ -573,6 +580,22 @@ static void pkt_stream_even_odd_sequence(struct test_spec *test)
>  	}
>  }
>  
> +static void release_even_odd_sequence(struct test_spec *test)
> +{
> +	struct pkt_stream *later_free_tx = test->ifobj_tx->xsk->pkt_stream;
> +	struct pkt_stream *later_free_rx = test->ifobj_rx->xsk->pkt_stream;
> +	int i;
> +
> +	for (i = 0; i < test->nb_sockets; i++) {
> +		/* later_free_{rx/tx} will be freed by restore_default() */
> +		if (test->ifobj_tx->xsk_arr[i].pkt_stream != later_free_tx)
> +			pkt_stream_delete(test->ifobj_tx->xsk_arr[i].pkt_stream);
> +		if (test->ifobj_rx->xsk_arr[i].pkt_stream != later_free_rx)
> +			pkt_stream_delete(test->ifobj_rx->xsk_arr[i].pkt_stream);
> +	}
> +
> +}
> +
>  static u64 pkt_get_addr(struct pkt *pkt, struct xsk_umem_info *umem)
>  {
>  	if (!pkt->valid)
> @@ -1874,6 +1897,7 @@ int testapp_stats_tx_invalid_descs(struct test_spec *test)
>  int testapp_stats_rx_full(struct test_spec *test)
>  {
>  	pkt_stream_replace(test, DEFAULT_UMEM_BUFFERS + DEFAULT_UMEM_BUFFERS / 2, MIN_PKT_SIZE);
> +	pkt_stream_delete(test->ifobj_rx->xsk->pkt_stream);
>  	test->ifobj_rx->xsk->pkt_stream = pkt_stream_generate(DEFAULT_UMEM_BUFFERS, MIN_PKT_SIZE);
>  
>  	test->ifobj_rx->xsk->rxqsize = DEFAULT_UMEM_BUFFERS;
> @@ -1885,6 +1909,7 @@ int testapp_stats_rx_full(struct test_spec *test)
>  int testapp_stats_fill_empty(struct test_spec *test)
>  {
>  	pkt_stream_replace(test, DEFAULT_UMEM_BUFFERS + DEFAULT_UMEM_BUFFERS / 2, MIN_PKT_SIZE);
> +	pkt_stream_delete(test->ifobj_rx->xsk->pkt_stream);
>  	test->ifobj_rx->xsk->pkt_stream = pkt_stream_generate(DEFAULT_UMEM_BUFFERS, MIN_PKT_SIZE);
>  
>  	test->ifobj_rx->use_fill_ring = false;
> @@ -2043,6 +2068,7 @@ int testapp_xdp_shared_umem(struct test_spec *test)
>  {
>  	struct xsk_xdp_progs *skel_rx = test->ifobj_rx->xdp_progs;
>  	struct xsk_xdp_progs *skel_tx = test->ifobj_tx->xdp_progs;
> +	int ret;
>  
>  	test->total_steps = 1;
>  	test->nb_sockets = 2;
> @@ -2053,7 +2079,11 @@ int testapp_xdp_shared_umem(struct test_spec *test)
>  
>  	pkt_stream_even_odd_sequence(test);
>  
> -	return testapp_validate_traffic(test);
> +	ret = testapp_validate_traffic(test);
> +
> +	release_even_odd_sequence(test);
> +
> +	return ret;
>  }
>  
>  int testapp_poll_txq_tmout(struct test_spec *test)
> 
> -- 
> 2.50.1
>