[PATCH 4.4 21/73] gre: do not pull header in ICMP error processing

Greg Kroah-Hartman
2016-05-17T01:57:00Z

From: Jiri Benc <jbenc@redhat.com>

[ Upstream commit b7f8fe251e4609e2a437bd2c2dea01e61db6849c ]

iptunnel_pull_header expects that IP header was already pulled; with this
expectation, it pulls the tunnel header. This is not true in gre_err.
Furthermore, ipv4_update_pmtu and ipv4_redirect expect that skb->data points
to the IP header.

We cannot pull the tunnel header in this path. It's just a matter of not
calling iptunnel_pull_header - we don't need any of its effects.

Fixes: bda7bb463436 ("gre: Allow multiple protocol listener for gre protocol.")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/ip_gre.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -180,6 +180,7 @@ static __be16 tnl_flags_to_gre_flags(__b
return flags;
}

+/* Fills in tpi and returns header length to be pulled. */
static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
bool *csum_err)
{
@@ -239,7 +240,7 @@ static int parse_gre_header(struct sk_bu
return -EINVAL;
}
}
- return iptunnel_pull_header(skb, hdr_len, tpi->proto);
+ return hdr_len;
}

static void ipgre_err(struct sk_buff *skb, u32 info,
@@ -342,7 +343,7 @@ static void gre_err(struct sk_buff *skb,
struct tnl_ptk_info tpi;
bool csum_err = false;

- if (parse_gre_header(skb, &tpi, &csum_err)) {
+ if (parse_gre_header(skb, &tpi, &csum_err) < 0) {
if (!csum_err) /* ignore csum errors. */
return;
}
@@ -420,6 +421,7 @@ static int gre_rcv(struct sk_buff *skb)
{
struct tnl_ptk_info tpi;
bool csum_err = false;
+ int hdr_len;

#ifdef CONFIG_NET_IPGRE_BROADCAST
if (ipv4_is_multicast(ip_hdr(skb)->daddr)) {
@@ -429,7 +431,10 @@ static int gre_rcv(struct sk_buff *skb)
}
#endif

- if (parse_gre_header(skb, &tpi, &csum_err) < 0)
+ hdr_len = parse_gre_header(skb, &tpi, &csum_err);
+ if (hdr_len < 0)
+ goto drop;
+ if (iptunnel_pull_header(skb, hdr_len, tpi.proto) < 0)
goto drop;

if (ipgre_rcv(skb, &tpi) == PACKET_RCVD)