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

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Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Marek Lindner" <mareklindner@...mailbox.ch>,
        "Martin Hundebøll" <martin@...deboll.net>,
        "Sven Eckelmann" <sven@...fation.org>
Subject: [PATCH 3.16 188/305] batman-adv: Use only queued fragments when
 merging

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

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

From: Sven Eckelmann <sven@...fation.org>

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@...fation.org>
Acked-by: Martin Hundebøll <martin@...deboll.net>
Signed-off-by: Marek Lindner <mareklindner@...mailbox.ch>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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;