Commit 29e98242 authored May 16, 2014 by Eric Dumazet Committed by David S. Miller May 16, 2014

net: gro: make sure skb->cb[] initial content has not to be zero



Starting from linux-3.13, GRO attempts to build full size skbs.

Problem is the commit assumed one particular field in skb->cb[]
was clean, but it is not the case on some stacked devices.

Timo reported a crash in case traffic is decrypted before
reaching a GRE device.

Fix this by initializing NAPI_GRO_CB(skb)->last at the right place,
this also removes one conditional.

Thanks a lot to Timo for providing full reports and bisecting this.

Fixes: 8a29111c ("net: gro: allow to build full sized skb")
Bisected-by: Timo Teras <timo.teras@iki.fi>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Timo Teräs <timo.teras@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 22fb22ea

net/core/dev.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -3951,6 +3951,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
		}
		NAPI_GRO_CB(skb)->count = 1;
		NAPI_GRO_CB(skb)->age = jiffies;
		NAPI_GRO_CB(skb)->last = skb;
		skb_shinfo(skb)->gso_size = skb_gro_len(skb);
		skb->next = napi->gro_list;
		napi->gro_list = skb;

net/core/skbuff.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -3076,7 +3076,7 @@ int skb_gro_receive(struct sk_buff *head, struct sk_buff skb)
		if (unlikely(p->len + len >= 65536))
		return -E2BIG;

		lp = NAPI_GRO_CB(p)->last ?: p;
		lp = NAPI_GRO_CB(p)->last;
		pinfo = skb_shinfo(lp);

		if (headlen <= offset) {
		@@ -3192,7 +3192,7 @@ merge:

		__skb_pull(skb, offset);

		if (!NAPI_GRO_CB(p)->last)
		if (NAPI_GRO_CB(p)->last == p)
		skb_shinfo(p)->frag_list = skb;
		else
		NAPI_GRO_CB(p)->last->next = skb;

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