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batman-adv: tp_meter: fix tp_vars reference leak in receiver shutdown

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The receiver shutdown timer handler, batadv_tp_receiver_shutdown(), is
responsible for releasing the tp_vars reference it holds. However, the
existing logic for coordinating this release with batadv_tp_stop_all() was
flawed.

timer_shutdown_sync() guarantees the timer will not fire again after it
returns, but it returns non-zero only when the timer was pending at the
time of the call. If the timer had already expired (and
batadv_tp_stop_all() would unsucessfully try to  rearm itself),
batadv_tp_stop_all() skips its batadv_tp_vars_put(), and
batadv_tp_receiver_shutdown() fails to put its own reference as well.

Fix this by introducing a new atomic variable receiving that is set to 1
when the receiver is initialized and cleared atomically with atomic_xchg()
by whichever side claims it first. Only the side that observes the
transition from 1 to 0 is responsible for releasing the tp_vars timer
reference, eliminating the uncertainty.

Cc: stable@kernel.org
Fixes: 3d3cf6a731 ("batman-adv: stop tp_meter sessions during mesh teardown")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
This commit is contained in:
Sven Eckelmann 2026-05-10 11:31:03 +02:00
parent 94f3b13316
commit 77098e4bea
No known key found for this signature in database
GPG Key ID: 4D0F772BD314F5CB
2 changed files with 14 additions and 2 deletions
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13
net/batman-adv/tp_meter.c
View File

@ -8,6 +8,7 @@
#include "main.h"
#include <linux/atomic.h>
#include <linux/bug.h>
#include <linux/build_bug.h>
#include <linux/byteorder/generic.h>
#include <linux/cache.h>
@ -1156,6 +1157,9 @@ static void batadv_tp_receiver_shutdown(struct timer_list *t)
spin_unlock_bh(&tp_vars->unacked_lock);
/* drop reference of timer */
if (WARN_ON(atomic_xchg(&tp_vars->receiving, 0) != 1))
return;
batadv_tp_vars_put(tp_vars);
}
@ -1374,6 +1378,7 @@ batadv_tp_init_recv(struct batadv_priv *bat_priv,
ether_addr_copy(tp_vars->other_end, icmp->orig);
tp_vars->role = BATADV_TP_RECEIVER;
atomic_set(&tp_vars->receiving, 1);
memcpy(tp_vars->session, icmp->session, sizeof(tp_vars->session));
tp_vars->last_recv = BATADV_TP_FIRST_SEQ;
tp_vars->bat_priv = bat_priv;
@ -1546,8 +1551,12 @@ void batadv_tp_stop_all(struct batadv_priv *bat_priv)
break;
case BATADV_TP_RECEIVER:
batadv_tp_list_detach(tp_var);
if (timer_shutdown_sync(&tp_var->timer))
batadv_tp_vars_put(tp_var);
timer_shutdown_sync(&tp_var->timer);
if (atomic_xchg(&tp_var->receiving, 0) != 1)
break;
batadv_tp_vars_put(tp_var);
break;
}

3
net/batman-adv/types.h
View File

@ -1323,6 +1323,9 @@ struct batadv_tp_vars {
/** @sending: sending binary semaphore: 1 if sending, 0 is not */
atomic_t sending;
/** @receiving: receiving binary semaphore: 1 if receiving, 0 is not */
atomic_t receiving;
/** @reason: reason for a stopped session */
enum batadv_tp_meter_reason reason;