taskstats: check nla_reserve() return

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=44621

Reported-by: <rucsoftsec@gmail.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/taskstats.c

@@ -436,6 +436,11 @@ static int cgroupstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
 
 	na = nla_reserve(rep_skb, CGROUPSTATS_TYPE_CGROUP_STATS,
 				sizeof(struct cgroupstats));
+	if (na == NULL) {
+		rc = -EMSGSIZE;
+		goto err;
+	}
+
 	stats = nla_data(na);
 	memset(stats, 0, sizeof(*stats));