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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org,
	Alexander Levin <alexander.levin@verizon.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Zhen Lei <thunder.leizhen@huawei.com>,
	Joe Korty <joe.korty@concurrent-rt.com>
Subject: [PATCH 4.4 09/11] futex: Avoid freeing an active timer
Date: Sun,  8 Aug 2021 09:22:44 +0200	[thread overview]
Message-ID: <20210808072217.637655944@linuxfoundation.org> (raw)
In-Reply-To: <20210808072217.322468704@linuxfoundation.org>

From: Thomas Gleixner <tglx@linutronix.de>

[ Upstream commit 97181f9bd57405b879403763284537e27d46963d ]

Alexander reported a hrtimer debug_object splat:

  ODEBUG: free active (active state 0) object type: hrtimer hint: hrtimer_wakeup (kernel/time/hrtimer.c:1423)

  debug_object_free (lib/debugobjects.c:603)
  destroy_hrtimer_on_stack (kernel/time/hrtimer.c:427)
  futex_lock_pi (kernel/futex.c:2740)
  do_futex (kernel/futex.c:3399)
  SyS_futex (kernel/futex.c:3447 kernel/futex.c:3415)
  do_syscall_64 (arch/x86/entry/common.c:284)
  entry_SYSCALL64_slow_path (arch/x86/entry/entry_64.S:249)

Which was caused by commit:

  cfafcd117da0 ("futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock()")

... losing the hrtimer_cancel() in the shuffle. Where previously the
hrtimer_cancel() was done by rt_mutex_slowlock() we now need to do it
manually.

Reported-by: Alexander Levin <alexander.levin@verizon.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: cfafcd117da0 ("futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock()")
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1704101802370.2906@nanos
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Acked-by: Joe Korty <joe.korty@concurrent-rt.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/futex.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2960,8 +2960,10 @@ out_unlock_put_key:
 out_put_key:
 	put_futex_key(&q.key);
 out:
-	if (to)
+	if (to) {
+		hrtimer_cancel(&to->timer);
 		destroy_hrtimer_on_stack(&to->timer);
+	}
 	return ret != -EINTR ? ret : -ERESTARTNOINTR;
 
 uaddr_faulted:



  parent reply	other threads:[~2021-08-08  7:24 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-08  7:22 [PATCH 4.4 00/11] 4.4.280-rc1 review Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 01/11] futex: Rename free_pi_state() to put_pi_state() Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 02/11] futex: Cleanup refcounting Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 03/11] futex,rt_mutex: Introduce rt_mutex_init_waiter() Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 04/11] futex: Pull rt_mutex_futex_unlock() out from under hb->lock Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 05/11] futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock() Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 06/11] futex: Futex_unlock_pi() determinism Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 07/11] rtmutex: Make wait_lock irq safe Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 08/11] futex: Handle transient "ownerless" rtmutex state correctly Greg Kroah-Hartman
2021-08-08  7:22 ` Greg Kroah-Hartman [this message]
2021-08-08  7:22 ` [PATCH 4.4 10/11] futex,rt_mutex: Fix rt_mutex_cleanup_proxy_lock() Greg Kroah-Hartman
2021-08-08  7:22 ` [PATCH 4.4 11/11] rcu: Update documentation of rcu_read_unlock() Greg Kroah-Hartman
2021-08-08 16:00 ` [PATCH 4.4 00/11] 4.4.280-rc1 review Guenter Roeck
2021-08-10 15:44   ` Greg Kroah-Hartman
2021-08-09 14:14 ` Naresh Kamboju
  -- strict thread matches above, loose matches on Subject: below --
2021-08-02 13:46 [PATCH 4.4 00/11] Fix a potential infinite loop in RT futex-pi scenarios Zhen Lei
2021-08-02 13:46 ` [PATCH 4.4 09/11] futex: Avoid freeing an active timer Zhen Lei

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