[PATCH net] ieee802154: lowpan_header_create check must check daddr

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

From: Willem de Bruijn <willemb@google.com>

Packet sockets may call dev_header_parse with NULL daddr. Make
lowpan_header_ops.create fail.

Fixes: 87a93e4eceb4 ("ieee802154: change needed headroom/tailroom")
Signed-off-by: Willem de Bruijn <willemb@google.com>

---

Re: function comment on packet socket address length: that is (now)
verified to be at least dev->addr_len.

It is customary to return -header_len on failure in .create(), but
not sure what that would be here, and any negative value is treated
the same by callers, so returning -EINVAL.

Is the return 0 on !ETH_P_IPV6 intentional, or should that also be
negative?
---
 net/ieee802154/6lowpan/tx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ieee802154/6lowpan/tx.c b/net/ieee802154/6lowpan/tx.c
index ca53efa17be1..8bec827081cd 100644
--- a/net/ieee802154/6lowpan/tx.c
+++ b/net/ieee802154/6lowpan/tx.c
@@ -48,6 +48,9 @@ int lowpan_header_create(struct sk_buff *skb, struct net_device *ldev,
 	const struct ipv6hdr *hdr = ipv6_hdr(skb);
 	struct neighbour *n;
 
+	if (!daddr)
+		return -EINVAL;
+
 	/* TODO:
 	 * if this package isn't ipv6 one, where should it be routed?
 	 */
-- 
2.20.1.415.g653613c723-goog