[PATCH 6.12.y] batman-adv: tp_meter: fix tp_num leak on kmalloc failure

[Sven Eckelmann <sven@narfation.org>]

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

Cc: stable@kernel.org
Fixes: 33a3bb4a3345 ("batman-adv: throughput meter implementation")
[ Context ]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/tp_meter.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/batman-adv/tp_meter.c b/net/batman-adv/tp_meter.c
index 7f3dd3c393e0..16da48b23f57 100644
--- a/net/batman-adv/tp_meter.c
+++ b/net/batman-adv/tp_meter.c
@@ -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