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 <[email protected]> --- fragmentation.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fragmentation.c b/fragmentation.c index 0ab228f..9e06457 100644 --- a/fragmentation.c +++ b/fragmentation.c @@ -433,7 +433,7 @@ 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 */ -- 2.1.3
