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Commit 22251c73 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ip_gre: fix a possible crash in parse_gre_header() 



pskb_may_pull() can change skb->head, so we must init iph/greh after
calling it.

Bug added in commit c5441932 (GRE: Refactor GRE tunneling code.)

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f8075a8c

net/ipv4/ip_gre.c

+5 −3
Original line number Diff line number Diff line
@@ -159,14 +159,14 @@ static int ip_gre_calc_hlen(__be16 o_flags) 
static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,

			    bool *csum_err, int *hdr_len)

{

	struct iphdr *iph = ip_hdr(skb);

	struct gre_base_hdr *greh;

	unsigned int ip_hlen = ip_hdrlen(skb);

	const struct gre_base_hdr *greh;

	__be32 *options;



	if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))

		return -EINVAL;



	greh = (struct gre_base_hdr *)((u8 *)iph + (iph->ihl << 2));

	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);

	if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))

		return -EINVAL;
@@ -176,6 +176,8 @@ static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, 
	if (!pskb_may_pull(skb, *hdr_len))

		return -EINVAL;



	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);



	tpi->proto = greh->protocol;



	options = (__be32 *)(greh + 1);