| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <87cymdsu0r.ffs@tglx>
Date: Mon, 12 Aug 2024 16:19:48 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: 朱恺乾 <zhukaiqian@...omi.com>, Daniel Lezcano
<daniel.lezcano@...aro.org>,
张嘉伟 <zhangjiawei8@...omi.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
王韬
<lingyue@...omi.com>, 熊亮 <xiongliang@...omi.com>,
"isaacmanjarres@...gle.com" <isaacmanjarres@...gle.com>, Frederic
Weisbecker <frederic@...nel.org>, Anna-Maria Behnsen
<anna-maria@...utronix.de>, 梁伟鹏
<weipengliang@...omi.com>, 翁金飞
<wengjinfei@...omi.com>
Subject: [PATCH] tick/broadcast: Plug clockevents replacement race
朱恺乾 reported and decoded the following race condition when a broadcast
device is replaced:
CPUA CPUB
__tick_broadcast_oneshot_control()
bc = tick_broadcast_device.evtdev;
tick_install_broadcast_device(dev)
clockevents_exchange_device(cur, dev)
shutdown(cur);
detach(cur);
cur->handler = noop;
tick_broadcast_device.evtdev = dev;
tick_broadcast_set_event(bc, next_event); <- FAIL: arms a detached device.
If the original broadcast device has a restricted interrupt affinity mask
and the last CPU in that mask goes offline then the BUG() in
tick_cleanup_dead_cpu() triggers because the clockevent device is not in
detached state.
The reason for this is that tick_install_broadcast_device() is not
serialized vs. tick broadcast operations.
The obvious cure is to serialize tick_install_broadcast_device() with
tick_broadcast_lock against a concurrent tick broadcast operation.
That requires to split clockevents_exchange_device() into two parts, one
which does the exchange, shutdown and detach operation and the other which
drops the module reference count. This is required because the module
reference cannot be dropped while holding tick_broadcast_lock.
Let clockevents_exchange_device() do both operations as before, but let the
broadcast device code take the two step approach and do the device
exchange under tick_broadcast_lock and drop the module reference count
after releasing it.
Fixes: f8381cba04ba ("[PATCH] tick-management: broadcast functionality")
Reported-by: 朱恺乾 <zhukaiqian@...omi.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
kernel/time/clockevents.c | 33 ++++++++++++++++++++-------------
kernel/time/tick-broadcast.c | 36 ++++++++++++++++++++++--------------
kernel/time/tick-internal.h | 2 ++
3 files changed, 44 insertions(+), 27 deletions(-)
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -557,34 +557,41 @@ void clockevents_handle_noop(struct cloc
{
}
-/**
- * clockevents_exchange_device - release and request clock devices
- * @old: device to release (can be NULL)
- * @new: device to request (can be NULL)
- *
- * Called from various tick functions with clockevents_lock held and
- * interrupts disabled.
- */
-void clockevents_exchange_device(struct clock_event_device *old,
- struct clock_event_device *new)
+void __clockevents_exchange_device(struct clock_event_device *old,
+ struct clock_event_device *new)
{
/*
* Caller releases a clock event device. We queue it into the
* released list and do a notify add later.
*/
if (old) {
- module_put(old->owner);
clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
list_move(&old->list, &clockevents_released);
}
if (new) {
- BUG_ON(!clockevent_state_detached(new));
+ WARN_ON(!clockevent_state_detached(new));
clockevents_shutdown(new);
}
}
/**
+ * clockevents_exchange_device - release and request clock devices
+ * @old: device to release (can be NULL)
+ * @new: device to request (can be NULL)
+ *
+ * Called from various tick functions with clockevents_lock held and
+ * interrupts disabled.
+ */
+void clockevents_exchange_device(struct clock_event_device *old,
+ struct clock_event_device *new)
+{
+ __clockevents_exchange_device(old, new);
+ if (old)
+ module_put(old->owner);
+}
+
+/**
* clockevents_suspend - suspend clock devices
*/
void clockevents_suspend(void)
@@ -650,7 +657,7 @@ void tick_cleanup_dead_cpu(int cpu)
if (cpumask_test_cpu(cpu, dev->cpumask) &&
cpumask_weight(dev->cpumask) == 1 &&
!tick_is_broadcast_device(dev)) {
- BUG_ON(!clockevent_state_detached(dev));
+ WARN_ON(!clockevent_state_detached(dev));
list_del(&dev->list);
}
}
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -162,23 +162,31 @@ static bool tick_set_oneshot_wakeup_devi
*/
void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
{
- struct clock_event_device *cur = tick_broadcast_device.evtdev;
+ struct clock_event_device *cur;
- if (tick_set_oneshot_wakeup_device(dev, cpu))
- return;
+ scoped_guard(raw_spinlock_irqsave, &tick_broadcast_lock) {
- if (!tick_check_broadcast_device(cur, dev))
- return;
+ if (tick_set_oneshot_wakeup_device(dev, cpu))
+ return;
- if (!try_module_get(dev->owner))
- return;
+ cur = tick_broadcast_device.evtdev;
+ if (!tick_check_broadcast_device(cur, dev))
+ return;
- clockevents_exchange_device(cur, dev);
+ if (!try_module_get(dev->owner))
+ return;
+
+ __clockevents_exchange_device(cur, dev);
+ if (cur)
+ cur->event_handler = clockevents_handle_noop;
+ WRITE_ONCE(tick_broadcast_device.evtdev, dev);
+ if (!cpumask_empty(tick_broadcast_mask))
+ tick_broadcast_start_periodic(dev);
+ }
+
+ /* Module release must be outside of the lock */
if (cur)
- cur->event_handler = clockevents_handle_noop;
- tick_broadcast_device.evtdev = dev;
- if (!cpumask_empty(tick_broadcast_mask))
- tick_broadcast_start_periodic(dev);
+ module_put(cur->owner);
if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
return;
@@ -1209,7 +1217,7 @@ int tick_broadcast_oneshot_active(void)
*/
bool tick_broadcast_oneshot_available(void)
{
- struct clock_event_device *bc = tick_broadcast_device.evtdev;
+ struct clock_event_device *bc = READ_ONCE(tick_broadcast_device.evtdev);
return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
}
@@ -1217,7 +1225,7 @@ bool tick_broadcast_oneshot_available(vo
#else
int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
{
- struct clock_event_device *bc = tick_broadcast_device.evtdev;
+ struct clock_event_device *bc = READ_ONCE(tick_broadcast_device.evtdev);
if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
return -EBUSY;
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -53,6 +53,8 @@ static inline void clockevent_set_state(
}
extern void clockevents_shutdown(struct clock_event_device *dev);
+extern void __clockevents_exchange_device(struct clock_event_device *old,
+ struct clock_event_device *new);
extern void clockevents_exchange_device(struct clock_event_device *old,
struct clock_event_device *new);
extern void clockevents_switch_state(struct clock_event_device *dev,
Powered by blists - more mailing lists