FAILED: patch "[PATCH] batman-adv: tt: reject oversized local TVLV buffers" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 1e9fab756f8395096d5bba7be0c373c4c8f5d165
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026052827-crate-spotter-3e8f@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1e9fab756f8395096d5bba7be0c373c4c8f5d165 Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <[email protected]>
Date: Sat, 2 May 2026 19:08:37 +0200
Subject: [PATCH] batman-adv: tt: reject oversized local TVLV buffers

The commit 3a359bf5c61d ("batman-adv: reject oversized global TT response buffers") added a check to ensure that a global return buffer size can be stored in an u16. The same buffer handling also exists for the local data buffer but was not touched.

A similar check should be also be in place for the local TVLV buffer. It doesn't have the similar attack surface because it is only generated from locally discovered MAC addresses but the dynamic nature could still cause temporarily to large buffers.

index 05cddcf994f6..06548dae1039 100644
@@ -877,12 +877,12 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 {
 	struct batadv_tvlv_tt_vlan_data *tt_vlan;
 	struct batadv_meshif_vlan *vlan;
+	size_t change_offset;
 	u16 num_vlan = 0;
 	u16 vlan_entries = 0;
 	u16 total_entries = 0;
 	u16 tvlv_len;
 	u8 *tt_change_ptr;
-	int change_offset;
 
 	spin_lock_bh(&bat_priv->meshif_vlan_list_lock);
 	hlist_for_each_entry(vlan, &bat_priv->meshif_vlan_list, list) {

@@ -900,8 +900,10 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 	if (*tt_len < 0)
 		*tt_len = batadv_tt_len(total_entries);
 
-	tvlv_len = *tt_len;
-	tvlv_len += change_offset;
+	if (check_add_overflow(*tt_len, change_offset, &tvlv_len)) {
+		tvlv_len = 0;
+		goto out;
+	}
 
 	*tt_data = kmalloc(tvlv_len, GFP_ATOMIC);
 	if (!*tt_data) {

commit 1e9fab756f8395096d5bba7be0c373c4c8f5d165 upstream.

The commit 3a359bf5c61d ("batman-adv: reject oversized global TT response buffers") added a check to ensure that a global return buffer size can be stored in an u16. The same buffer handling also exists for the local data buffer but was not touched.

A similar check should be also be in place for the local TVLV buffer. It doesn't have the similar attack surface because it is only generated from locally discovered MAC addresses but the dynamic nature could still cause temporarily to large buffers.

---
 net/batman-adv/translation-table.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

index f1e93a6048203..6c40d690ac6c3 100644
@@ -924,12 +924,12 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 {
 	struct batadv_tvlv_tt_vlan_data *tt_vlan;
 	struct batadv_softif_vlan *vlan;
+	size_t change_offset;
 	u16 num_vlan = 0;
 	u16 vlan_entries = 0;
 	u16 total_entries = 0;
 	u16 tvlv_len;
 	u8 *tt_change_ptr;
-	int change_offset;
 
 	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
 	hlist_for_each_entry(vlan, &bat_priv->softif_vlan_list, list) {

@@ -948,8 +948,10 @@ batadv_tt_prepare_tvlv_local_data(struct batadv_priv *bat_priv,
 	if (*tt_len < 0)
 		*tt_len = batadv_tt_len(total_entries);
 
-	tvlv_len = *tt_len;
-	tvlv_len += change_offset;
+	if (check_add_overflow(*tt_len, change_offset, &tvlv_len)) {
+		tvlv_len = 0;
+		goto out;
+	}
 
 	*tt_data = kmalloc(tvlv_len, GFP_ATOMIC);
 	if (!*tt_data) {

2.47.3