Re: mac80211 truesize bugs

Once that is cured, I think we can detect this better, by adding a
carefully constructed assertion to pskb_expand_head().  Basically, the
idea is, if "nhead" or "ntail" are non-zero, and there is a socket
still attached to the SKB, print a warning message.

Something like:

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4fe605f..9bfca08 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c

@@ -699,6 +699,12 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 	if (skb_shared(skb))
 		BUG();
 
+	if (unlikely((nhead || ntail) && skb->sk)) {
+		printk(KERN_ERR "SKB BUG: Illegal pskb expand (%d:%d) "
+		       "with socket attached\n",
+		       nhead, ntail);
+	}