bpf: mark bpf_dummy_struct_ops.test_1 parameter as nullable

In the Linux kernel, the following vulnerability has been resolved:

bpf: mark bpf_dummy_struct_ops.test_1 parameter as nullable

Test case dummy_st_ops/dummy_init_ret_value passes NULL as the first

parameter of the test_1() function. Mark this parameter as nullable to

make verifier aware of such possibility.

Otherwise, NULL check in the test_1() code:

SEC("struct_ops/test_1")

int BPF_PROG(test_1, struct bpf_dummy_ops_state *state)

{

if (!state)

return ...;

... access state ...

}

Might be removed by verifier, thus triggering NULL pointer dereference

under certain conditions.