selftests/bpf: Avoid running unprivileged tests with alignment requirements

Some architectures have strict alignment requirements. In that case,
the BPF verifier detects if a program has unaligned accesses and
rejects them. A user can pass BPF_F_ANY_ALIGNMENT to a program to
override this check. That, however, will only work when a privileged
user loads a program. A unprivileged user loading a program with this
flag will be rejected prior entering the verifier.

Hence, it does not make sense to load unprivileged programs without
strict alignment when testing the verifier. This patch avoids exactly
that.

Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>

Author: bjoto

tools/testing/selftests/bpf/test_verifier.c

@@ -1152,9 +1152,15 @@ static void get_unpriv_disabled()
 
 static bool test_as_unpriv(struct bpf_test *test)
 {
-	return !test->prog_type ||
-	       test->prog_type == BPF_PROG_TYPE_SOCKET_FILTER ||
-	       test->prog_type == BPF_PROG_TYPE_CGROUP_SKB;
+	bool req_aligned = false;
+
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	req_aligned = test->flags & F_NEEDS_EFFICIENT_UNALIGNED_ACCESS;
+#endif
+	return (!test->prog_type ||
+		test->prog_type == BPF_PROG_TYPE_SOCKET_FILTER ||
+		test->prog_type == BPF_PROG_TYPE_CGROUP_SKB) &&
+		!req_aligned;
 }
 
 static int do_test(bool unpriv, unsigned int from, unsigned int to)