audit: consistently record PIDs with task_tgid_nr()

Unfortunately we record PIDs in audit records using a variety of
methods despite the correct way being the use of task_tgid_nr().
This patch converts all of these callers, except for the case of
AUDIT_SET in audit_receive_msg() (see the comment in the code).

Reported-by: Jeff Vander Stoep <jeffv@google.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

kernel/audit.c

@@ -877,6 +877,12 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 				return err;
 		}
 		if (s.mask & AUDIT_STATUS_PID) {
+			/* NOTE: we are using task_tgid_vnr() below because
+			 *       the s.pid value is relative to the namespace
+			 *       of the caller; at present this doesn't matter
+			 *       much since you can really only run auditd
+			 *       from the initial pid namespace, but something
+			 *       to keep in mind if this changes */
 			int new_pid = s.pid;
 			pid_t requesting_pid = task_tgid_vnr(current);
 
@@ -1917,7 +1923,7 @@ void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
 			 " euid=%u suid=%u fsuid=%u"
 			 " egid=%u sgid=%u fsgid=%u tty=%s ses=%u",
 			 task_ppid_nr(tsk),
-			 task_pid_nr(tsk),
+			 task_tgid_nr(tsk),
 			 from_kuid(&init_user_ns, audit_get_loginuid(tsk)),
 			 from_kuid(&init_user_ns, cred->uid),
 			 from_kgid(&init_user_ns, cred->gid),