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authorPrashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>2018-07-13 14:40:50 +0900
committerDavid S. Miller <davem@davemloft.net>2018-07-16 13:39:47 -0700
commitb7ed879425be371905d856410d19e9a42a62bcf3 (patch)
treebfc68d99f78c5897875eced15f2328252a9c23dd /net/ipv6/ip6_gre.c
parent6e8cfd6d9d8049e2fd5b2de8a328519dc58ea1e6 (diff)
downloadlinux-b7ed879425be371905d856410d19e9a42a62bcf3.tar.bz2
net: ip6_gre: get ipv6hdr after skb_cow_head()
A KASAN:use-after-free bug was found related to ip6-erspan while running selftests/net/ip6_gre_headroom.sh It happens because of following sequence: - ipv6hdr pointer is obtained from skb - skb_cow_head() is called, skb->head memory is reallocated - old data is accessed using ipv6hdr pointer skb_cow_head() call was added in e41c7c68ea77 ("ip6erspan: make sure enough headroom at xmit."), but looking at the history there was a chance of similar bug because gre_handle_offloads() and pskb_trim() can also reallocate skb->head memory. Fixes tag points to commit which introduced possibility of this bug. This patch moves ipv6hdr pointer assignment after skb_cow_head() call. Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support") Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp> Reviewed-by: Greg Rose <gvrose8192@gmail.com> Acked-by: William Tu <u9012063@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/ip6_gre.c')
-rw-r--r--net/ipv6/ip6_gre.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index c8cf2fdbb13b..cd2cfb04e5d8 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -927,7 +927,6 @@ tx_err:
static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
struct net_device *dev)
{
- struct ipv6hdr *ipv6h = ipv6_hdr(skb);
struct ip6_tnl *t = netdev_priv(dev);
struct dst_entry *dst = skb_dst(skb);
struct net_device_stats *stats;
@@ -1010,6 +1009,8 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
goto tx_err;
}
} else {
+ struct ipv6hdr *ipv6h = ipv6_hdr(skb);
+
switch (skb->protocol) {
case htons(ETH_P_IP):
memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));