[3.16.y-ckt stable] Patch "batman-adv: Unify fragment size calculation" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    batman-adv: Unify fragment size calculation

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt5.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From ee5079798f5eaf1bc22646329e2efa785d9d4bf2 Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <sven at narfation.org>
Date: Sat, 20 Dec 2014 13:48:56 +0100
Subject: batman-adv: Unify fragment size calculation

commit 0402e444cd199389b7fe47be68a67b817e09e097 upstream.

The fragmentation code was replaced in 610bfc6bc99bc83680d190ebc69359a05fc7f605
("batman-adv: Receive fragmented packets and merge") by an implementation which
can handle up to 16 fragments of a packet. The packet is prepared for the split
in fragments by the function batadv_frag_send_packet and the actual split is
done by batadv_frag_create.

Both functions calculate the size of a fragment themself. But their calculation
differs because batadv_frag_send_packet also subtracts ETH_HLEN. Therefore,
the check in batadv_frag_send_packet "can a full fragment can be created?" may
return true even when batadv_frag_create cannot create a full fragment.

The function batadv_frag_create doesn't check the size of the skb before
splitting it and therefore might try to create a larger fragment than the
remaining buffer. This creates an integer underflow and an invalid len is given
to skb_split.

Signed-off-by: Sven Eckelmann <sven at narfation.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/batman-adv/fragmentation.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
index 57dd88db6bb7..d2b6d5066c33 100644
--- a/net/batman-adv/fragmentation.c
+++ b/net/batman-adv/fragmentation.c
@@ -434,7 +434,7 @@ bool batadv_frag_send_packet(struct sk_buff *skb,
 	 * fragments larger than BATADV_FRAG_MAX_FRAG_SIZE
 	 */
 	mtu = min_t(unsigned, mtu, BATADV_FRAG_MAX_FRAG_SIZE);
-	max_fragment_size = (mtu - header_size - ETH_HLEN);
+	max_fragment_size = mtu - header_size;
 	max_packet_size = max_fragment_size * BATADV_FRAG_MAX_FRAGMENTS;

 	/* Don't even try to fragment, if we need more than 16 fragments */
--
2.1.4