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Subject[ 16/41] ipsec: be careful of non existing mac headers
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <eric.dumazet@gmail.com>

[ 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>
---
include/linux/skbuff.h | 10 ++++++++++
net/ipv4/xfrm4_mode_beet.c | 5 +----
net/ipv4/xfrm4_mode_tunnel.c | 6 ++----
net/ipv6/xfrm6_mode_beet.c | 6 +-----
net/ipv6/xfrm6_mode_tunnel.c | 6 ++----
5 files changed, 16 insertions(+), 17 deletions(-)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1453,6 +1453,16 @@ static inline void skb_set_mac_header(st
}
#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);
--- 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_

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);

--- a/net/ipv4/xfrm4_mode_tunnel.c
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -66,7 +66,6 @@ static int xfrm4_mode_tunnel_output(stru

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(struc
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:
--- 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
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_

__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);

--- a/net/ipv6/xfrm6_mode_tunnel.c
+++ b/net/ipv6/xfrm6_mode_tunnel.c
@@ -63,7 +63,6 @@ static int xfrm6_mode_tunnel_output(stru
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(struc
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:

--
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