selftests/bpf: Use bpf_num_possible_cpus() in per-cpu map allocations

bpf_map_value_size() uses num_possible_cpus() to determine map size, but
some of the tests only allocate enough memory for online cpus. This
results in out-of-bound writes in userspace during bpf(BPF_MAP_LOOKUP_ELEM)
syscalls in cases when number of online cpus is lower than the number of
possible cpus. Fix by switching from get_nprocs_conf() to
bpf_num_possible_cpus() when determining the number of processors in
these tests (test_progs/netcnt and test_cgroup_storage).

Signed-off-by: Artem Savkov <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/netcnt.c b/tools/testing/selftests/bpf/prog_tests/netcnt.c
index 954964f0ac3d..d3915c58d0e1 100644
--- a/tools/testing/selftests/bpf/prog_tests/netcnt.c
+++ b/tools/testing/selftests/bpf/prog_tests/netcnt.c
@@ -25,7 +25,7 @@ void serial_test_netcnt(void)
 	if (!ASSERT_OK_PTR(skel, "netcnt_prog__open_and_load"))
 		return;
 
-	nproc = get_nprocs_conf();
+	nproc = bpf_num_possible_cpus();
 	percpu_netcnt = malloc(sizeof(*percpu_netcnt) * nproc);
 	if (!ASSERT_OK_PTR(percpu_netcnt, "malloc(percpu_netcnt)"))
 		goto err;