Commit 662c3e2d authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add a test to verify previous stacksafe() fix 



A selftest is added such that without the previous patch,
a crash can happen. With the previous patch, the test can
run successfully. The new test is written in a way which
mimics original crash case:
  main_prog
    static_prog_1
      static_prog_2
where static_prog_1 has different paths to static_prog_2
and some path has stack allocated and some other path
does not. A stacksafe() checking in static_prog_2()
triggered the crash.

Signed-off-by: default avatarYonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240812214852.214037-1-yonghong.song@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent bed2eb96

tools/testing/selftests/bpf/progs/iters.c

+54 −0
Original line number Diff line number Diff line
@@ -1432,4 +1432,58 @@ int iter_arr_with_actual_elem_count(const void *ctx) 
	return sum;

}



__u32 upper, select_n, result;

__u64 global;



static __noinline bool nest_2(char *str)

{

	/* some insns (including branch insns) to ensure stacksafe() is triggered

	 * in nest_2(). This way, stacksafe() can compare frame associated with nest_1().

	 */

	if (str[0] == 't')

		return true;

	if (str[1] == 'e')

		return true;

	if (str[2] == 's')

		return true;

	if (str[3] == 't')

		return true;

	return false;

}



static __noinline bool nest_1(int n)

{

	/* case 0: allocate stack, case 1: no allocate stack */

	switch (n) {

	case 0: {

		char comm[16];



		if (bpf_get_current_comm(comm, 16))

			return false;

		return nest_2(comm);

	}

	case 1:

		return nest_2((char *)&global);

	default:

		return false;

	}

}



SEC("raw_tp")

__success

int iter_subprog_check_stacksafe(const void *ctx)

{

	long i;



	bpf_for(i, 0, upper) {

		if (!nest_1(select_n)) {

			result = 1;

			return 0;

		}

	}



	result = 2;

	return 0;

}



char _license[] SEC("license") = "GPL";