audit: deliver signal_info regarless of syscall

When a process signals the audit daemon (shutdown, rotate, resume,
reconfig) but syscall auditing is not enabled, we still want to know the
identity of the process sending the signal to the audit daemon.

Move audit_signal_info() out of syscall auditing to general auditing but
create a new function audit_signal_info_syscall() to take care of the
syscall dependent parts for when syscall auditing is enabled.

Please see the github kernel audit issue
https://github.com/linux-audit/audit-kernel/issues/111

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
diff --git a/kernel/audit.c b/kernel/audit.c
index b96bf69..67399ff 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -2274,6 +2274,33 @@ int audit_set_loginuid(kuid_t loginuid)
 }
 
 /**
+ * audit_signal_info - record signal info for shutting down audit subsystem
+ * @sig: signal value
+ * @t: task being signaled
+ *
+ * If the audit subsystem is being terminated, record the task (pid)
+ * and uid that is doing that.
+ */
+int audit_signal_info(int sig, struct task_struct *t)
+{
+	kuid_t uid = current_uid(), auid;
+
+	if (auditd_test_task(t) &&
+	    (sig == SIGTERM || sig == SIGHUP ||
+	     sig == SIGUSR1 || sig == SIGUSR2)) {
+		audit_sig_pid = task_tgid_nr(current);
+		auid = audit_get_loginuid(current);
+		if (uid_valid(auid))
+			audit_sig_uid = auid;
+		else
+			audit_sig_uid = uid;
+		security_task_getsecid(current, &audit_sig_sid);
+	}
+
+	return audit_signal_info_syscall(t);
+}
+
+/**
  * audit_log_end - end one audit record
  * @ab: the audit_buffer
  *