[PATCH 3.16 188/305] batman-adv: Use only queued fragments when merging

From: Ben Hutchings
Date: Sun Feb 03 2019 - 08:58:16 EST


3.16.63-rc1 review patch. If anyone has any objections, please let me know.

------------------

From: Sven Eckelmann <sven@xxxxxxxxxxxxx>

commit 83e8b87721f21b26b843633caca8ef453e943623 upstream.

The fragment queueing code now validates the total_size of each fragment,
checks when enough fragments are queued to allow to merge them into a
single packet and if the fragments have the correct size. Therefore, it is
not required to have any other parameter for the merging function than a
list of queued fragments.

This change should avoid problems like in the past when the different skb
from the list and the function parameter were mixed incorrectly.

Signed-off-by: Sven Eckelmann <sven@xxxxxxxxxxxxx>
Acked-by: Martin HundebÃll <martin@xxxxxxxxxxxxx>
Signed-off-by: Marek Lindner <mareklindner@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
net/batman-adv/fragmentation.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

--- a/net/batman-adv/fragmentation.c
+++ b/net/batman-adv/fragmentation.c
@@ -234,19 +234,13 @@ err:
* Returns the merged skb or NULL on error.
*/
static struct sk_buff *
-batadv_frag_merge_packets(struct hlist_head *chain, struct sk_buff *skb)
+batadv_frag_merge_packets(struct hlist_head *chain)
{
struct batadv_frag_packet *packet;
struct batadv_frag_list_entry *entry;
struct sk_buff *skb_out = NULL;
int size, hdr_size = sizeof(struct batadv_frag_packet);

- /* Make sure incoming skb has non-bogus data. */
- packet = (struct batadv_frag_packet *)skb->data;
- size = ntohs(packet->total_size);
- if (size > batadv_frag_size_limit())
- goto free;
-
/* Remove first entry, as this is the destination for the rest of the
* fragments.
*/
@@ -255,6 +249,9 @@ batadv_frag_merge_packets(struct hlist_h
skb_out = entry->skb;
kfree(entry);

+ packet = (struct batadv_frag_packet *)skb_out->data;
+ size = ntohs(packet->total_size);
+
/* Make room for the rest of the fragments. */
if (pskb_expand_head(skb_out, 0, size - skb_out->len, GFP_ATOMIC) < 0) {
kfree_skb(skb_out);
@@ -311,7 +308,7 @@ bool batadv_frag_skb_buffer(struct sk_bu
if (hlist_empty(&head))
goto out;

- skb_out = batadv_frag_merge_packets(&head, *skb);
+ skb_out = batadv_frag_merge_packets(&head);
if (!skb_out)
goto out_err;