net: ieee802154: 6lowpan: fix frag reassembly

BugLink: https://bugs.launchpad.net/bugs/1818806

commit f18fa5de upstream.

This patch initialize stack variables which are used in
frag_lowpan_compare_key to zero. In my case there are padding bytes in the
structures ieee802154_addr as well in frag_lowpan_compare_key. Otherwise
the key variable contains random bytes. The result is that a compare of
two keys by memcmp works incorrect.

Fixes: 648700f7 ("inet: frags: use rhashtables for reassembly units")
Signed-off-by: Alexander Aring <aring@mojatatu.com>
Reported-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

net/ieee802154/6lowpan/6lowpan_i.h

@@ -19,8 +19,8 @@ typedef unsigned __bitwise__ lowpan_rx_result;
 struct frag_lowpan_compare_key {
 	u16 tag;
 	u16 d_size;
-	const struct ieee802154_addr src;
-	const struct ieee802154_addr dst;
+	struct ieee802154_addr src;
+	struct ieee802154_addr dst;
 };
 
 /* Equivalent of ipv4 struct ipq

net/ieee802154/6lowpan/reassembly.c

@@ -74,14 +74,14 @@ fq_find(struct net *net, const struct lowpan_802154_cb *cb,
 {
 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
 		net_ieee802154_lowpan(net);
-	struct frag_lowpan_compare_key key = {
-		.tag = cb->d_tag,
-		.d_size = cb->d_size,
-		.src = *src,
-		.dst = *dst,
-	};
+	struct frag_lowpan_compare_key key = {};
 	struct inet_frag_queue *q;
 
+	key.tag = cb->d_tag;
+	key.d_size = cb->d_size;
+	key.src = *src;
+	key.dst = *dst;
+
 	q = inet_frag_find(&ieee802154_lowpan->frags, &key);
 	if (IS_ERR_OR_NULL(q)) {
 		inet_frag_maybe_warn_overflow(q, pr_fmt());
@@ -372,7 +372,7 @@ int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
 	struct lowpan_frag_queue *fq;
 	struct net *net = dev_net(skb->dev);
 	struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
-	struct ieee802154_hdr hdr;
+	struct ieee802154_hdr hdr = {};
 	int err;
 
 	if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)