audit: use task_tgid_nr() instead of task_pid_nr()

In a few audit records, PIDs were being recorded with task_pid_nr()
instead of task_tgid_nr().

$ grep "task_pid_nr" kernel/audit*.c
audit.c:       task_pid_nr(current),
auditfilter.c: pid = task_pid_nr(current);
auditsc.c:     audit_log_format(ab, " pid=%u", task_pid_nr(current));

For single-thread applications, the process id (pid) and the thread
group id (tgid) are the same. However, on multi-thread applications,
task_pid_nr() returns the current thread id (user-space's TID), while
task_tgid_nr() returns the main thread id (user-space's PID). Since
the users are more interested in the process id (pid), rather than the
thread id (tid), this patch converts these callers to the correct method.

Link: https://github.com/linux-audit/audit-kernel/issues/126

Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Ricardo Robaina <rrobaina@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

kernel/audit.c

@@ -1612,7 +1612,7 @@ static void audit_log_multicast(int group, const char *op, int err)
 	cred = current_cred();
 	tty = audit_get_tty();
 	audit_log_format(ab, "pid=%u uid=%u auid=%u tty=%s ses=%u",
-			 task_pid_nr(current),
+			 task_tgid_nr(current),
 			 from_kuid(&init_user_ns, cred->uid),
 			 from_kuid(&init_user_ns, audit_get_loginuid(current)),
 			 tty ? tty_name(tty) : "(none)",

kernel/auditfilter.c

@@ -1344,7 +1344,7 @@ int audit_filter(int msgtype, unsigned int listtype)
 
 			switch (f->type) {
 			case AUDIT_PID:
-				pid = task_pid_nr(current);
+				pid = task_tgid_nr(current);
 				result = audit_comparator(pid, f->op, f->val);
 				break;
 			case AUDIT_UID:

kernel/auditsc.c

@@ -2933,7 +2933,7 @@ void __audit_log_nfcfg(const char *name, u8 af, unsigned int nentries,
 	audit_log_format(ab, "table=%s family=%u entries=%u op=%s",
 			 name, af, nentries, audit_nfcfgs[op].s);
 
-	audit_log_format(ab, " pid=%u", task_pid_nr(current));
+	audit_log_format(ab, " pid=%u", task_tgid_nr(current));
 	audit_log_task_context(ab); /* subj= */
 	audit_log_format(ab, " comm=");
 	audit_log_untrustedstring(ab, get_task_comm(comm, current));