zdtm: set the dumpable flag after setuid (v2)

Otherwise we will not able to access /proc/pid/* for the process.

v2: s/__NR_WAIT4/__NR_setresuid

Cc: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/live/static/seccomp_filter.c

@@ -97,7 +97,12 @@ int main(int argc, char ** argv)
 		if (filter_syscall(__NR_ptrace) < 0)
 			_exit(1);
 
-		if (filter_syscall(__NR_prctl) < 0)
+		/*
+		 * The idea is to have a syscall that is used in restore_creds,
+		 * so we can make sure seccomp is actually suspended when that
+		 * is called.
+		 */
+		if (filter_syscall(__NR_setresuid) < 0)
 			_exit(1);
 
 		setuid(1000);
@@ -115,6 +120,18 @@ int main(int argc, char ** argv)
 			_exit(1);
 		}
 
+		prctl(PR_SET_DUMPABLE, 1);
+
+		if (write(sk, &c, 1) != 1) {
+			pr_perror("write");
+			_exit(1);
+		}
+
+		if (read(sk, &c, 1) != 1) {
+			pr_perror("read");
+			_exit(1);
+		}
+
 		/* We expect to be killed by our policy above. */
 		ptrace(PTRACE_TRACEME);
 
@@ -132,6 +149,15 @@ int main(int argc, char ** argv)
 	test_daemon();
 	test_waitsig();
 
+	if (write(sk, &c, 1) != 1) {
+		pr_perror("write");
+		goto err;
+	}
+	if ((ret = read(sk, &c, 1)) != 1) {
+		pr_perror("read %d", ret);
+		goto err;
+	}
+
 	mode = get_seccomp_mode(pid);
 	if (write(sk, &c, 1) != 1) {
 		pr_perror("write");