On 06/02, David Vernet wrote:
> In a recent patch, we taught the verifier that trusted PTR_TO_BTF_ID can
> never be NULL. This prevents the verifier from incorrectly failing to
> load certain programs where it gets confused and thinks a reference
> isn't dropped because it incorrectly assumes that a branch exists in
> which a NULL PTR_TO_BTF_ID pointer is never released.
>
> This patch adds a testcase that verifies this cannot happen.
>
> Signed-off-by: David Vernet <void@xxxxxxxxxxxxx>
Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
I hope someone else can look at the actual change. It looks good to
me conceptually, but not sure what other parts it might affect.
> ---
> .../selftests/bpf/prog_tests/cpumask.c | 1 +
> .../selftests/bpf/progs/cpumask_success.c | 24 +++++++++++++++++++
> 2 files changed, 25 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/cpumask.c b/tools/testing/selftests/bpf/prog_tests/cpumask.c
> index cdf4acc18e4c..d89191440fb1 100644
> --- a/tools/testing/selftests/bpf/prog_tests/cpumask.c
> +++ b/tools/testing/selftests/bpf/prog_tests/cpumask.c
> @@ -70,5 +70,6 @@ void test_cpumask(void)
> verify_success(cpumask_success_testcases[i]);
> }
>
> + RUN_TESTS(cpumask_success);
> RUN_TESTS(cpumask_failure);
> }
> diff --git a/tools/testing/selftests/bpf/progs/cpumask_success.c b/tools/testing/selftests/bpf/progs/cpumask_success.c
> index 2fcdd7f68ac7..602a88b03dbc 100644
> --- a/tools/testing/selftests/bpf/progs/cpumask_success.c
> +++ b/tools/testing/selftests/bpf/progs/cpumask_success.c
> @@ -5,6 +5,7 @@
> #include <bpf/bpf_tracing.h>
> #include <bpf/bpf_helpers.h>
>
> +#include "bpf_misc.h"
> #include "cpumask_common.h"
>
> char _license[] SEC("license") = "GPL";
> @@ -426,3 +427,26 @@ int BPF_PROG(test_global_mask_rcu, struct task_struct *task, u64 clone_flags)
>
> return 0;
> }
> +
> +SEC("tp_btf/task_newtask")
> +__success
> +int BPF_PROG(test_refcount_null_tracking, struct task_struct *task, u64 clone_flags)
> +{
> + struct bpf_cpumask *mask1, *mask2;
> +
> + mask1 = bpf_cpumask_create();
> + mask2 = bpf_cpumask_create();
> +
> + if (!mask1 || !mask2)
> + goto free_masks_return;
> +
> + bpf_cpumask_test_cpu(0, (const struct cpumask *)mask1);
> + bpf_cpumask_test_cpu(0, (const struct cpumask *)mask2);
> +
> +free_masks_return:
> + if (mask1)
> + bpf_cpumask_release(mask1);
> + if (mask2)
> + bpf_cpumask_release(mask2);
> + return 0;
> +}
> --
> 2.40.1
>
