From: Luxiao Xu Date: Mon, 11 May 2026 16:52:09 +0000 (+0200) Subject: batman-adv: fix tp_meter counter underflow during shutdown X-Git-Tag: v7.1-rc5~40^2~56^2~13 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=94f3b133168d1c49895e7cc6afbcf1cc0b354602;p=thirdparty%2Flinux.git batman-adv: fix tp_meter counter underflow during shutdown batadv_tp_sender_shutdown() unconditionally decrements the "sending" atomic counter. If multiple paths (e.g. timeout, user cancel, and normal finish) call this function, the counter can underflow to -1. Since the sender logic treats any non-zero value as "still sending", a negative value causes the sender kthread to loop indefinitely. This leads to a use-after-free when the interface is removed while the zombie thread is still active. Fix this by using atomic_xchg() to ensure the counter only transitions from 1 to 0 once. Fixes: 33a3bb4a3345 ("batman-adv: throughput meter implementation") Cc: stable@kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Signed-off-by: Luxiao Xu Signed-off-by: Ren Wei [sven: added missing change in batadv_tp_send] Signed-off-by: Sven Eckelmann --- diff --git a/net/batman-adv/tp_meter.c b/net/batman-adv/tp_meter.c index 066c76113fc43..a4397aa881dd4 100644 --- a/net/batman-adv/tp_meter.c +++ b/net/batman-adv/tp_meter.c @@ -451,7 +451,7 @@ static void batadv_tp_sender_end(struct batadv_priv *bat_priv, static void batadv_tp_sender_shutdown(struct batadv_tp_vars *tp_vars, enum batadv_tp_meter_reason reason) { - if (!atomic_dec_and_test(&tp_vars->sending)) + if (atomic_xchg(&tp_vars->sending, 0) != 1) return; tp_vars->reason = reason; @@ -885,7 +885,7 @@ static int batadv_tp_send(void *arg) "Meter: %s() cannot send packets (%d)\n", __func__, err); /* ensure nobody else tries to stop the thread now */ - if (atomic_dec_and_test(&tp_vars->sending)) + if (atomic_xchg(&tp_vars->sending, 0) == 1) tp_vars->reason = err; break; }