ipsec: be careful of non existing mac headers

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>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 50db9b0..ae86ade 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1465,6 +1465,16 @@ static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
 }
 #endif /* NET_SKBUFF_DATA_USES_OFFSET */
 
+static inline void skb_mac_header_rebuild(struct sk_buff *skb)
+{
+       if (skb_mac_header_was_set(skb)) {
+               const unsigned char *old_mac = skb_mac_header(skb);
+
+               skb_set_mac_header(skb, -skb->mac_len);
+               memmove(skb_mac_header(skb), old_mac, skb->mac_len);
+       }
+}
+
 static inline int skb_checksum_start_offset(const struct sk_buff *skb)
 {
        return skb->csum_start - skb_headroom(skb);

diff --git a/net/ipv4/xfrm4_mode_beet.c b/net/ipv4/xfrm4_mode_beet.c
index 6341818..e3db3f9 100644 (file)
--- a/net/ipv4/xfrm4_mode_beet.c
+++ b/net/ipv4/xfrm4_mode_beet.c
@@ -110,10 +110,7 @@ static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
 
        skb_push(skb, sizeof(*iph));
        skb_reset_network_header(skb);
-
-       memmove(skb->data - skb->mac_len, skb_mac_header(skb),
-               skb->mac_len);
-       skb_set_mac_header(skb, -skb->mac_len);
+       skb_mac_header_rebuild(skb);
 
        xfrm4_beet_make_header(skb);
 

diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
index 534972e..ed4bf11 100644 (file)
--- a/net/ipv4/xfrm4_mode_tunnel.c
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -66,7 +66,6 @@ static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
 
 static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 {
-       const unsigned char *old_mac;
        int err = -EINVAL;
 
        if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
@@ -84,10 +83,9 @@ static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
        if (!(x->props.flags & XFRM_STATE_NOECN))
                ipip_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:

diff --git a/net/ipv6/xfrm6_mode_beet.c b/net/ipv6/xfrm6_mode_beet.c
index a81ce94..9949a35 100644 (file)
--- 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 261e6e6..9f2095b 100644 (file)
--- 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: