taskstats: cgroupstats_user_cmd() may leak on error

If prepare_reply() succeeds we have allocated memory for 'rep_skb'.  If
nla_reserve() then subsequently fails and returns NULL we fail to release
the memory we allocated, thus causing a leak.
Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Cc: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/taskstats.c

@@ -445,6 +445,7 @@ 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) {
+		nlmsg_free(rep_skb);
 		rc = -EMSGSIZE;
 		goto err;
 	}