From: Sven Eckelmann <[email protected]> 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: [email protected] Fixes: 3d3cf6a7314a ("batman-adv: stop tp_meter sessions during mesh teardown") Signed-off-by: Sven Eckelmann <[email protected]> Signed-off-by: Simon Wunderlich <[email protected]> --- net/batman-adv/tp_meter.c | 13 +++++++++++-- net/batman-adv/types.h | 3 +++ 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/net/batman-adv/tp_meter.c b/net/batman-adv/tp_meter.c index a4397aa881dd4..ca6c3f6374bc5 100644 --- a/net/batman-adv/tp_meter.c +++ b/net/batman-adv/tp_meter.c @@ -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; } diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index daa06f4211542..b9c0b77791226 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -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; -- 2.47.3
