diff options
| author | Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp> | 2018-07-13 14:40:50 +0900 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-07-16 13:39:47 -0700 |
| commit | b7ed879425be371905d856410d19e9a42a62bcf3 (patch) | |
| tree | bfc68d99f78c5897875eced15f2328252a9c23dd | |
| parent | 6e8cfd6d9d8049e2fd5b2de8a328519dc58ea1e6 (diff) | |
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>
| -rw-r--r-- | net/ipv6/ip6_gre.c | 3 |
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)); |