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Commit 3174fed9 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net: skb_condense() can also deal with empty skbs 



It seems attackers can also send UDP packets with no payload at all.

skb_condense() can still be a win in this case.

It will be possible to replace the custom code in tcp_add_backlog()
to get full benefit from skb_condense()

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5ac9efbe

net/core/skbuff.c

+13 −9
Original line number Diff line number Diff line
@@ -4946,16 +4946,20 @@ EXPORT_SYMBOL(pskb_extract); 
 */

void skb_condense(struct sk_buff *skb)

{

	if (!skb->data_len ||

	    skb->data_len > skb->end - skb->tail ||

	if (skb->data_len) {

		if (skb->data_len > skb->end - skb->tail ||

		    skb_cloned(skb))

			return;



		/* Nice, we can free page frag(s) right now */

		__pskb_pull_tail(skb, skb->data_len);



	/* Now adjust skb->truesize, since __pskb_pull_tail() does

	 * not do this.

	}

	/* At this point, skb->truesize might be over estimated,

	 * because skb had a fragment, and fragments do not tell

	 * their truesize.

	 * When we pulled its content into skb->head, fragment

	 * was freed, but __pskb_pull_tail() could not possibly

	 * adjust skb->truesize, not knowing the frag truesize.

	 */

	skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));

}