[PATCH stable backport] Bluetooth: 6lowpan: Fix memory corruption of ipv6 destination address

[PATCH stable backport] Bluetooth: 6lowpan: Fix memory corruption of ipv6 destination address

[Glenn Ruben Bakke]

Backport for v4.5 and v4.6 of
commit 55441070ca1cbd47ce1ad2959bbf4b47aed9b83b upstream.

The memcpy of ipv6 header destination address to the skb control block
(sbk->cb) in header_create() results in currupted memory when bt_xmit()
is issued. The skb->cb is "released" in the return of header_create()
making room for lower layer to minipulate the skb->cb.

The value retrieved in bt_xmit is not persistent across header creation
and sending, and the lower layer will overwrite portions of skb->cb,
making the copied destination address wrong.

The memory corruption will lead to non-working multicast as the first 4
bytes of the copied destination address is replaced by a value that
resolves into a non-multicast prefix.

This fix removes the dependency on the skb control block between header
creation and send, by moving the destination address memcpy to the send
function path (setup_create, which is called from bt_xmit).

Signed-off-by: Glenn Ruben Bakke <glenn.ruben.bakke@nordicsemi.no>
---
 net/bluetooth/6lowpan.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index 8a4cc2f..e45cb91 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -431,15 +431,18 @@ static int setup_header(struct sk_buff *skb, struct net_device *netdev,
 			bdaddr_t *peer_addr, u8 *peer_addr_type)
 {
 	struct in6_addr ipv6_daddr;
+	struct ipv6hdr *hdr;
 	struct lowpan_dev *dev;
 	struct lowpan_peer *peer;
 	bdaddr_t addr, *any = BDADDR_ANY;
 	u8 *daddr = any->b;
 	int err, status = 0;
 
+	hdr = ipv6_hdr(skb);
+
 	dev = lowpan_dev(netdev);
 
-	memcpy(&ipv6_daddr, &lowpan_cb(skb)->addr, sizeof(ipv6_daddr));
+	memcpy(&ipv6_daddr, &hdr->daddr, sizeof(ipv6_daddr));
 
 	if (ipv6_addr_is_multicast(&ipv6_daddr)) {
 		lowpan_cb(skb)->chan = NULL;
@@ -489,15 +492,9 @@ static int header_create(struct sk_buff *skb, struct net_device *netdev,
 			 unsigned short type, const void *_daddr,
 			 const void *_saddr, unsigned int len)
 {
-	struct ipv6hdr *hdr;
-
 	if (type != ETH_P_IPV6)
 		return -EINVAL;
 
-	hdr = ipv6_hdr(skb);
-
-	memcpy(&lowpan_cb(skb)->addr, &hdr->daddr, sizeof(struct in6_addr));
-
 	return 0;
 }
 
-- 
2.5.0

Re: [PATCH stable backport] Bluetooth: 6lowpan: Fix memory corruption of ipv6 destination address

[Jukka Rissanen]

Hi Glenn,

On Tue, 2016-05-31 at 12:23 +0200, Glenn Ruben Bakke wrote:
> Backport for v4.5 and v4.6 of
> commit 55441070ca1cbd47ce1ad2959bbf4b47aed9b83b upstream.
> 
> The memcpy of ipv6 header destination address to the skb control
> block
> (sbk->cb) in header_create() results in currupted memory when
> bt_xmit()
> is issued. The skb->cb is "released" in the return of header_create()
> making room for lower layer to minipulate the skb->cb.
> 
> The value retrieved in bt_xmit is not persistent across header
> creation
> and sending, and the lower layer will overwrite portions of skb->cb,
> making the copied destination address wrong.
> 
> The memory corruption will lead to non-working multicast as the first
> 4
> bytes of the copied destination address is replaced by a value that
> resolves into a non-multicast prefix.
> 
> This fix removes the dependency on the skb control block between
> header
> creation and send, by moving the destination address memcpy to the
> send
> function path (setup_create, which is called from bt_xmit).
> 
> Signed-off-by: Glenn Ruben Bakke <glenn.ruben.bakke@nordicsemi.no>
> ---

Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>


Cheers,
Jukka