net: fixes for skb_send_sock

A couple fixes to new skb_send_sock infrastructure. However, no users
currently exist for this code (adding user in next handful of patches)
so it should not be possible to trigger a panic with existing in-kernel
code.

Fixes: 306b13eb3c ("proto_ops: Add locked held versions of sendmsg and sendpage")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -2285,7 +2285,7 @@ do_frag_list:
 
 		slen = min_t(int, len, skb_headlen(skb) - offset);
 		kv.iov_base = skb->data + offset;
-		kv.iov_len = len;
+		kv.iov_len = slen;
 		memset(&msg, 0, sizeof(msg));
 
 		ret = kernel_sendmsg_locked(sk, &msg, &kv, 1, slen);