ipsec: be careful of non existing mac headers

[ Upstream commit 03606895cd98c0a628b17324fd7b5ff15db7e3cd ]

Niccolo Belli reported ipsec crashes in case we handle a frame without
mac header (atm in his case)

Before copying mac header, better make sure it is present.

Bugzilla reference:  https://bugzilla.kernel.org/show_bug.cgi?id=42809

Reported-by: Niccolò Belli <darkbasic@linuxsystems.it>
Tested-by: Niccolò Belli <darkbasic@linuxsystems.it>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 3 insertions, 9 deletions

diff --git a/net/ipv6/xfrm6_mode_beet.c b/net/ipv6/xfrm6_mode_beet.c
index 3437d7d4eed..f37cba9e689 100644
--- a/net/ipv6/xfrm6_mode_beet.c
+++ b/net/ipv6/xfrm6_mode_beet.c
@@ -80,7 +80,6 @@ static int xfrm6_beet_output(struct xfrm_state *x, struct sk_buff *skb)
 static int xfrm6_beet_input(struct xfrm_state *x, struct sk_buff *skb)
 {
         struct ipv6hdr *ip6h;
-        const unsigned char *old_mac;
         int size = sizeof(struct ipv6hdr);
         int err;
 
@@ -90,10 +89,7 @@ static int xfrm6_beet_input(struct xfrm_state *x, struct sk_buff *skb)
 
         __skb_push(skb, size);
         skb_reset_network_header(skb);
-
-        old_mac = skb_mac_header(skb);
-        skb_set_mac_header(skb, -skb->mac_len);
-        memmove(skb_mac_header(skb), old_mac, skb->mac_len);
+        skb_mac_header_rebuild(skb);
 
         xfrm6_beet_make_header(skb);
 
diff --git a/net/ipv6/xfrm6_mode_tunnel.c b/net/ipv6/xfrm6_mode_tunnel.c
index 4d6edff0498..23ecd68a5e6 100644
--- a/net/ipv6/xfrm6_mode_tunnel.c
+++ b/net/ipv6/xfrm6_mode_tunnel.c
@@ -63,7 +63,6 @@ static int xfrm6_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
 static int xfrm6_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 {
         int err = -EINVAL;
-        const unsigned char *old_mac;
 
         if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPV6)
                 goto out;
@@ -80,10 +79,9 @@ static int xfrm6_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
         if (!(x->props.flags & XFRM_STATE_NOECN))
                 ipip6_ecn_decapsulate(skb);
 
-        old_mac = skb_mac_header(skb);
-        skb_set_mac_header(skb, -skb->mac_len);
-        memmove(skb_mac_header(skb), old_mac, skb->mac_len);
         skb_reset_network_header(skb);
+        skb_mac_header_rebuild(skb);
+
         err = 0;
 
 out: