FAILED: patch "[PATCH] batman-adv: tp_meter: fix tp_num leak on kmalloc failure" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x ce425dd05d0fe7594930a0fb103634f35ac47bb6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026051520-serve-zit-cadd@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From ce425dd05d0fe7594930a0fb103634f35ac47bb6 Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <[email protected]>
Date: Wed, 6 May 2026 22:20:49 +0200
Subject: [PATCH] batman-adv: tp_meter: fix tp_num leak on kmalloc failure

When batadv_tp_start() or batadv_tp_init_recv() fail to allocate a new tp_vars object, the previously incremented bat_priv->tp_num counter is never decremented. This causes tp_num to drift upward on each allocation failure. Since only BATADV_TP_MAX_NUM sessions can be started and the count is never reduced for these failed allocations, it causes to an exhaustion of throughput meter sessions. In worst case, no new throughput meter session can be started until the mesh interface is removed.

The error handling must decrement tp_num releasing the lock and aborting the creation of an throughput meter session

index 58ca59a2799e..066c76113fc4 100644
@@ -994,6 +994,7 @@ void batadv_tp_start(struct batadv_priv *bat_priv, const u8 *dst,
 
 	tp_vars = kmalloc_obj(*tp_vars, GFP_ATOMIC);
 	if (!tp_vars) {
+		atomic_dec(&bat_priv->tp_num);
 		spin_unlock_bh(&bat_priv->tp_list_lock);
 		batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
 			   "Meter: %s cannot allocate list elements\n",

@@ -1366,8 +1367,10 @@ batadv_tp_init_recv(struct batadv_priv *bat_priv,
 	}
 
 	tp_vars = kmalloc_obj(*tp_vars, GFP_ATOMIC);
-	if (!tp_vars)
+	if (!tp_vars) {
+		atomic_dec(&bat_priv->tp_num);
 		goto out_unlock;
+	}
 
 	ether_addr_copy(tp_vars->other_end, icmp->orig);
 	tp_vars->role = BATADV_TP_RECEIVER;

commit ce425dd05d0fe7594930a0fb103634f35ac47bb6 upstream.

When batadv_tp_start() or batadv_tp_init_recv() fail to allocate a new tp_vars object, the previously incremented bat_priv->tp_num counter is never decremented. This causes tp_num to drift upward on each allocation failure. Since only BATADV_TP_MAX_NUM sessions can be started and the count is never reduced for these failed allocations, it causes to an exhaustion of throughput meter sessions. In worst case, no new throughput meter session can be started until the mesh interface is removed.

The error handling must decrement tp_num releasing the lock and aborting the creation of an throughput meter session

---
 net/batman-adv/tp_meter.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

index 56b9fe97b3b4..0eb9eccfc1e8 100644
@@ -969,6 +969,7 @@ void batadv_tp_start(struct batadv_priv *bat_priv, const u8 *dst,
 
 	tp_vars = kmalloc(sizeof(*tp_vars), GFP_ATOMIC);
 	if (!tp_vars) {
+		atomic_dec(&bat_priv->tp_num);
 		spin_unlock_bh(&bat_priv->tp_list_lock);
 		batadv_dbg(BATADV_DBG_TP_METER, bat_priv,
 			   "Meter: %s cannot allocate list elements\n",

@@ -1344,8 +1345,10 @@ batadv_tp_init_recv(struct batadv_priv *bat_priv,
 	}
 
 	tp_vars = kmalloc(sizeof(*tp_vars), GFP_ATOMIC);
-	if (!tp_vars)
+	if (!tp_vars) {
+		atomic_dec(&bat_priv->tp_num);
 		goto out_unlock;
+	}
 
 	ether_addr_copy(tp_vars->other_end, icmp->orig);
 	tp_vars->role = BATADV_TP_RECEIVER;

2.47.3