From: Sven Eckelmann Date: Sat, 20 Dec 2014 12:48:56 +0000 (+0100) Subject: batman-adv: Unify fragment size calculation X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=0402e444cd199389b7fe47be68a67b817e09e097;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git batman-adv: Unify fragment size calculation 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 Signed-off-by: David S. Miller --- diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c index 8af3461d18d2..00f9e144cc97 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 */