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Commit b4e3cef7 authored by Li RongQing's avatar Li RongQing Committed by David S. Miller
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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: default avatarLi RongQing <roy.qing.li@gmail.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid 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));