Commit b4e3cef7 authored Oct 18, 2014 by Li RongQing Committed by David S. Miller Oct 18, 2014

ipv4: fix a potential use after free in gre_offload.c



pskb_may_pull() may change skb->data and make greh pointer oboslete;
so need to reassign greh;
but since first calling pskb_may_pull already ensured that skb->data
has enough space for greh, so move the reference of greh before second
calling pskb_may_pull(), to avoid reassign greh.

Fixes: 7a7ffbab("ipv4: fix tunneled VM traffic over hw VXLAN/GRE GSO NIC")
Cc: Wei-Chun Chao <weichunc@plumgrid.com>
Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 815afe17

net/ipv4/gre_offload.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -55,13 +55,13 @@ static struct sk_buff gre_gso_segment(struct sk_buff skb,
		if (csum)
		skb->encap_hdr_csum = 1;

		if (unlikely(!pskb_may_pull(skb, ghl)))
		goto out;

		/* setup inner skb. */
		skb->protocol = greh->protocol;
		skb->encapsulation = 0;

		if (unlikely(!pskb_may_pull(skb, ghl)))
		goto out;

		__skb_pull(skb, ghl);
		skb_reset_mac_header(skb);
		skb_set_network_header(skb, skb_inner_network_offset(skb));

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