linux-kernel - [PATCH 4.5 086/128] Bluetooth: 6lowpan: Fix memory corruption of ipv6 destination address

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Date:	Sun,  5 Jun 2016 15:24:01 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Glenn Ruben Bakke <glenn.ruben.bakke@...dicsemi.no>,
	Jukka Rissanen <jukka.rissanen@...ux.intel.com>,
	Marcel Holtmann <marcel@...tmann.org>
Subject: [PATCH 4.5 086/128] Bluetooth: 6lowpan: Fix memory corruption of ipv6 destination address

4.5-stable review patch.  If anyone has any objections, please let me know.

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

From: Glenn Ruben Bakke <glennrubenbakke@...dicsemi.no>

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@...dicsemi.no>
Acked-by: Jukka Rissanen <jukka.rissanen@...ux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/bluetooth/6lowpan.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -431,15 +431,18 @@ static int setup_header(struct sk_buff *
 			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
 			 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;
 }