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selftests/bpf: Add test for non-NULLable PTR_TO_BTF_IDs

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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@manifault.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20230602150112.1494194-2-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
David Vernet 2023-06-02 10:01:12 -05:00 • committed by Alexei Starovoitov
parent 51302c951c
commit f904c67876
2 changed files with 25 additions and 0 deletions
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1
tools/testing/selftests/bpf/prog_tests/cpumask.c
View file

@ -70,5 +70,6 @@ void test_cpumask(void)
verify_success(cpumask_success_testcases[i]); verify_success(cpumask_success_testcases[i]);
} }
RUN_TESTS(cpumask_success);
RUN_TESTS(cpumask_failure); RUN_TESTS(cpumask_failure);
} }

24
tools/testing/selftests/bpf/progs/cpumask_success.c
View file

@ -5,6 +5,7 @@
#include <bpf/bpf_tracing.h> #include <bpf/bpf_tracing.h>
#include <bpf/bpf_helpers.h> #include <bpf/bpf_helpers.h>
#include "bpf_misc.h"
#include "cpumask_common.h" #include "cpumask_common.h"
char _license[] SEC("license") = "GPL"; 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; 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;
}