linux-kernel - [PATCH 3.2 153/185] 6lowpan: Uncompression of traffic class field was incorrect

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Message-ID: <lsq.1388282924.16018583@decadent.org.uk>
Date:	Sun, 29 Dec 2013 03:08:44 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
	"Jukka Rissanen" <jukka.rissanen@...ux.intel.com>
Subject: [PATCH 3.2 153/185] 6lowpan: Uncompression of traffic class field
 was  incorrect

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Jukka Rissanen <jukka.rissanen@...ux.intel.com>

[ Upstream commit 1188f05497e7bd2f2614b99c54adfbe7413d5749 ]

If priority/traffic class field in IPv6 header is set (seen when
using ssh), the uncompression sets the TC and Flow fields incorrectly.

Example:

This is IPv6 header of a sent packet. Note the priority/TC (=1) in
the first byte.

00000000: 61 00 00 00 00 2c 06 40 fe 80 00 00 00 00 00 00
00000010: 02 02 72 ff fe c6 42 10 fe 80 00 00 00 00 00 00
00000020: 02 1e ab ff fe 4c 52 57

This gets compressed like this in the sending side

00000000: 72 31 04 06 02 1e ab ff fe 4c 52 57 ec c2 00 16
00000010: aa 2d fe 92 86 4e be c6 ....

In the receiving end, the packet gets uncompressed to this
IPv6 header

00000000: 60 06 06 02 00 2a 1e 40 fe 80 00 00 00 00 00 00
00000010: 02 02 72 ff fe c6 42 10 fe 80 00 00 00 00 00 00
00000020: ab ff fe 4c 52 57 ec c2

First four bytes are set incorrectly and we have also lost
two bytes from destination address.

The fix is to switch the case values in switch statement
when checking the TC field.

Signed-off-by: Jukka Rissanen <jukka.rissanen@...ux.intel.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/ieee802154/6lowpan.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
index 19d6aef..5d42df2 100644
--- a/net/ieee802154/6lowpan.c
+++ b/net/ieee802154/6lowpan.c
@@ -563,7 +563,7 @@ lowpan_process_data(struct sk_buff *skb)
 	 * Traffic class carried in-line
 	 * ECN + DSCP (1 byte), Flow Label is elided
 	 */
-	case 1: /* 10b */
+	case 2: /* 10b */
 		if (!skb->len)
 			goto drop;
 		tmp = lowpan_fetch_skb_u8(skb);
@@ -576,7 +576,7 @@ lowpan_process_data(struct sk_buff *skb)
 	 * Flow Label carried in-line
 	 * ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
 	 */
-	case 2: /* 01b */
+	case 1: /* 01b */
 		if (!skb->len)
 			goto drop;
 		tmp = lowpan_fetch_skb_u8(skb);

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