netfilter: ctnetlink: memleak in filter initialization error path

Release the filter object in case of error.

Fixes: cb8aa9a3 ("netfilter: ctnetlink: add kernel side filtering for dump")
Reported-by: syzbot+38b8b548a851a01793c5@syzkaller.appspotmail.com
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_netlink.c

@@ -939,7 +939,8 @@ ctnetlink_alloc_filter(const struct nlattr * const cda[], u8 family)
 			filter->mark.mask = 0xffffffff;
 		}
 	} else if (cda[CTA_MARK_MASK]) {
-		return ERR_PTR(-EINVAL);
+		err = -EINVAL;
+		goto err_filter;
 	}
 #endif
 	if (!cda[CTA_FILTER])
@@ -947,15 +948,17 @@ ctnetlink_alloc_filter(const struct nlattr * const cda[], u8 family)
 
 	err = ctnetlink_parse_zone(cda[CTA_ZONE], &filter->zone);
 	if (err < 0)
-		return ERR_PTR(err);
+		goto err_filter;
 
 	err = ctnetlink_parse_filter(cda[CTA_FILTER], filter);
 	if (err < 0)
-		return ERR_PTR(err);
+		goto err_filter;
 
 	if (filter->orig_flags) {
-		if (!cda[CTA_TUPLE_ORIG])
-			return ERR_PTR(-EINVAL);
+		if (!cda[CTA_TUPLE_ORIG]) {
+			err = -EINVAL;
+			goto err_filter;
+		}
 
 		err = ctnetlink_parse_tuple_filter(cda, &filter->orig,
 						   CTA_TUPLE_ORIG,
@@ -963,23 +966,32 @@ ctnetlink_alloc_filter(const struct nlattr * const cda[], u8 family)
 						   &filter->zone,
 						   filter->orig_flags);
 		if (err < 0)
-			return ERR_PTR(err);
+			goto err_filter;
 	}
 
 	if (filter->reply_flags) {
-		if (!cda[CTA_TUPLE_REPLY])
-			return ERR_PTR(-EINVAL);
+		if (!cda[CTA_TUPLE_REPLY]) {
+			err = -EINVAL;
+			goto err_filter;
+		}
 
 		err = ctnetlink_parse_tuple_filter(cda, &filter->reply,
 						   CTA_TUPLE_REPLY,
 						   filter->family,
 						   &filter->zone,
 						   filter->orig_flags);
-		if (err < 0)
-			return ERR_PTR(err);
+		if (err < 0) {
+			err = -EINVAL;
+			goto err_filter;
+		}
 	}
 
 	return filter;
+
+err_filter:
+	kfree(filter);
+
+	return ERR_PTR(err);
 }
 
 static bool ctnetlink_needs_filter(u8 family, const struct nlattr * const *cda)