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

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
...@@ -159,14 +159,14 @@ static int ip_gre_calc_hlen(__be16 o_flags) ...@@ -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, static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
bool *csum_err, int *hdr_len) bool *csum_err, int *hdr_len)
{ {
struct iphdr *iph = ip_hdr(skb); unsigned int ip_hlen = ip_hdrlen(skb);
struct gre_base_hdr *greh; const struct gre_base_hdr *greh;
__be32 *options; __be32 *options;
if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr)))) if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
return -EINVAL; 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))) if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
return -EINVAL; return -EINVAL;
...@@ -176,6 +176,8 @@ static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, ...@@ -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)) if (!pskb_may_pull(skb, *hdr_len))
return -EINVAL; return -EINVAL;
greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
tpi->proto = greh->protocol; tpi->proto = greh->protocol;
options = (__be32 *)(greh + 1); options = (__be32 *)(greh + 1);
......
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