Re: [PATCH bpf-next v6 11/15] selftests/bpf: test_xsk: Don't exit immediately when workers fail

[bot+bpf-ci@kernel.org]

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```
commit f89231e503dc0b97c81f4bb32d28532fb3471acd
Author: Bastien Curutchet (eBPF Foundation) <bastien.curutchet@bootlin.com>

selftests/bpf: test_xsk: Don't exit immediately when workers fail

This commit converts the test program from using exit_with_error()
(which immediately terminates) to proper error propagation through
return values. This allows the test suite to continue running after
failures.

> diff --git a/tools/testing/selftests/bpf/test_xsk.c b/tools/testing/selftests/bpf/test_xsk.c
> index 2c955e109..2c392d5b9 100644
> --- a/tools/testing/selftests/bpf/test_xsk.c
> +++ b/tools/testing/selftests/bpf/test_xsk.c

[ ... ]

> @@ -759,7 +761,7 @@ static bool is_metadata_correct(struct pkt *pkt, void *buffer, u64 addr)
>  	return true;
>  }
>
> -static bool is_adjust_tail_supported(struct xsk_xdp_progs *skel_rx)
> +static int is_adjust_tail_supported(struct xsk_xdp_progs *skel_rx, bool *supported)
>  {
>  	struct bpf_map *data_map;
>  	int adjust_value = 0;
> @@ -769,19 +771,21 @@ static bool is_adjust_tail_supported(struct xsk_xdp_progs *skel_rx)
>  	data_map = bpf_object__find_map_by_name(skel_rx->obj, "xsk_xdp_.bss");
>  	if (!data_map || !bpf_map__is_internal(data_map)) {
>  		ksft_print_msg("Error: could not find bss section of XDP program\n");
> -		exit_with_error(errno);
> +		return -EINVAL;
>  	}
>
>  	ret = bpf_map_lookup_elem(bpf_map__fd(data_map), &key, &adjust_value);
>  	if (ret) {
>  		ksft_print_msg("Error: bpf_map_lookup_elem failed with error %d\n", ret);
> -		exit_with_error(errno);
> +		return ret;
>  	}
>
>  	/* Set the 'adjust_value' variable to -EOPNOTSUPP in the XDP program if the adjust_tail
>  	 * helper is not supported. Skip the adjust_tail test case in this scenario.
>  	 */
> -	return adjust_value != -EOPNOTSUPP;
> +	*supported = adjust_value != -EOPNOTSUPP;
> +
> +	return 0;
>  }

[ ... ]

> @@ -1584,29 +1614,41 @@ void *worker_testapp_validate_rx(void *arg)
>  	int err;
>
>  	if (test->current_step == 1) {
> -		thread_common_ops(test, ifobject);
> +		err = thread_common_ops(test, ifobject);
>  	} else {
>  		xsk_clear_xskmap(ifobject->xskmap);
>  		err = xsk_update_xskmap(ifobject->xskmap, ifobject->xsk->xsk, 0);
> -		if (err) {
> +		if (err)
>  			ksft_print_msg("Error: Failed to update xskmap, error %s\n",
>  				       strerror(-err));
> -			exit_with_error(-err);
> -		}
>  	}
>
>  	pthread_barrier_wait(&barr);
>
> +	/* We leave only now in case of error to avoid getting stuck in the barrier */
> +	if (err) {
> +		test->fail = true;
> +		pthread_exit(NULL);
> +	}
> +
>  	err = receive_pkts(test);
>
>  	if (!err && ifobject->validation_func)
>  		err = ifobject->validation_func(ifobject);
>
>  	if (err) {
> -		if (test->adjust_tail && !is_adjust_tail_supported(ifobject->xdp_progs))
> -			test->adjust_tail_support = false;
> -		else
> +		if (!test->adjust_tail) {
>  			test->fail = true;
> +		} else {
> +			bool supported;
> +
> +			if (is_adjust_tail_supported(ifobject->xdp_progs, &supported))
> +				test->fail = true;
> +			if (!supported)
> +				test->adjust_tail_support = false;
> +			else
> +				test->fail = true;
> +		}
>  	}

Can the 'supported' variable be read uninitialized here? When
is_adjust_tail_supported() returns an error (non-zero), it doesn't
write to the *supported output parameter. The function returns early
from either the data_map check or bpf_map_lookup_elem() failure without
setting *supported. Then the code unconditionally checks "if (!supported)"
which would read uninitialized stack memory.

The control flow is:
  is_adjust_tail_supported() returns error
  -> test->fail = true is set
  -> execution continues to "if (!supported)"
  -> reads uninitialized 'supported' variable

Should this be structured with an else clause to only check 'supported'
when is_adjust_tail_supported() returns success?


```

---
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In-Reply-To-Subject: `selftests/bpf: test_xsk: Don't exit immediately when workers fail`
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/18910697393