The following commit has been merged in the master branch: commit 0402e444cd199389b7fe47be68a67b817e09e097 Author: Sven Eckelmann sven@narfation.org Date: Sat Dec 20 13:48:56 2014 +0100
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 sven@narfation.org Signed-off-by: David S. Miller davem@davemloft.net
diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c index 8af3461..00f9e14 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 */
linux-merge@lists.open-mesh.org