[PATCH AUTOSEL 4.14 100/103] ip_gre: fix parsing gre header in ipgre_err

Sasha Levin
2019-11-08T11:56:11Z

From: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>

[ Upstream commit b0350d51f001e6edc13ee4f253b98b50b05dd401 ]

gre_parse_header stops parsing when csum_err is encountered, which means
tpi->key is undefined and ip_tunnel_lookup will return NULL improperly.

This patch introduce a NULL pointer as csum_err parameter. Even when
csum_err is encountered, it won't return error and continue parsing gre
header as expected.

Fixes: 9f57c67c379d ("gre: Remove support for sharing GRE protocol hook.")
Reported-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/gre_demux.c | 7 ++++---
net/ipv4/ip_gre.c | 9 +++------
2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index b798862b6be5d..7efe740c06ebf 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -86,13 +86,14 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,

options = (__be32 *)(greh + 1);
if (greh->flags & GRE_CSUM) {
- if (skb_checksum_simple_validate(skb)) {
+ if (!skb_checksum_simple_validate(skb)) {
+ skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
+ null_compute_pseudo);
+ } else if (csum_err) {
*csum_err = true;
return -EINVAL;
}

- skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
- null_compute_pseudo);
options++;
}

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 347be2ea78d4a..f8d3a7ddf62af 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -230,13 +230,10 @@ static void gre_err(struct sk_buff *skb, u32 info)
const int type = icmp_hdr(skb)->type;
const int code = icmp_hdr(skb)->code;
struct tnl_ptk_info tpi;
- bool csum_err = false;

- if (gre_parse_header(skb, &tpi, &csum_err, htons(ETH_P_IP),
- iph->ihl * 4) < 0) {
- if (!csum_err) /* ignore csum errors. */
- return;
- }
+ if (gre_parse_header(skb, &tpi, NULL, htons(ETH_P_IP),
+ iph->ihl * 4) < 0)
+ return;

if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
ipv4_update_pmtu(skb, dev_net(skb->dev), info,
--
2.20.1