Commit 248e23b5 authored Feb 12, 2017 by Sven Eckelmann Committed by Simon Wunderlich Feb 21, 2017

batman-adv: Fix double free during fragment merge error

The function batadv_frag_skb_buffer was supposed not to consume the skbuff
on errors. This was followed in the helper function
batadv_frag_insert_packet when the skb would potentially be inserted in the
fragment queue. But it could happen that the next helper function
batadv_frag_merge_packets would try to merge the fragments and fail. This
results in a kfree_skb of all the enqueued fragments (including the just
inserted one). batadv_recv_frag_packet would detect the error in
batadv_frag_skb_buffer and try to free the skb again.

The behavior of batadv_frag_skb_buffer (and its helper
batadv_frag_insert_packet) must therefore be changed to always consume the
skbuff to have a common behavior and avoid the double kfree_skb.

Fixes: 610bfc6b ("batman-adv: Receive fragmented packets and merge")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

parent 4ea33ef0

net/batman-adv/fragmentation.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -239,8 +239,10 @@ static bool batadv_frag_insert_packet(struct batadv_orig_node *orig_node,
		spin_unlock_bh(&chain->lock);

		err:
		if (!ret)
		if (!ret) {
		kfree(frag_entry_new);
		kfree_skb(skb);
		}

		return ret;
		}
		@@ -313,7 +315,7 @@ batadv_frag_merge_packets(struct hlist_head *chain)
		*
		* There are three possible outcomes: 1) Packet is merged: Return true and
		* set skb to merged packet; 2) Packet is buffered: Return true and set skb
		* to NULL; 3) Error: Return false and leave skb as is.
		* to NULL; 3) Error: Return false and free skb.
		*
		* Return: true when packet is merged or buffered, false when skb is not not
		* used.
		@@ -338,9 +340,9 @@ bool batadv_frag_skb_buffer(struct sk_buff **skb,
		goto out_err;

		out:
		*skb = skb_out;
		ret = true;
		out_err:
		*skb = skb_out;
		return ret;
		}