Repository : ssh://git@open-mesh.org/batman-adv

On branch : next

commit eddbc3d739ddb87111a2c30893e19f3176b6e1a6 Author: Sven Eckelmann sven@narfation.org Date: Mon Dec 1 13:59:44 2014 +0100

batman-adv: Unify fragment size calculation

The fragmentation code was replaced in 9b3eab61754d74a93c9840c296013fe3b4a1b606 ("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 if 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@narfation.org Acked-by: Martin Hundebøll martin@hundeboll.net Signed-off-by: Marek Lindner mareklindner@neomailbox.ch

eddbc3d739ddb87111a2c30893e19f3176b6e1a6 fragmentation.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fragmentation.c b/fragmentation.c index 8af3461..00f9e14 100644 --- a/fragmentation.c +++ b/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 */