This is a note to let you know that I've just added the patch titled
futex: Avoid freeing an active timer
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
futex-avoid-freeing-an-active-timer.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Mon Mar 29 07:48:09 AM CEST 2021
From: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Date: Sun, 28 Mar 2021 22:42:00 +0200
Subject: futex: Avoid freeing an active timer
To: stable@xxxxxxxxxxxxxxx
Cc: Lee Jones <lee.jones@xxxxxxxxxx>, "Luis Claudio R. Goncalves" <lgoncalv@xxxxxxxxxx>, Florian Fainelli <f.fainelli@xxxxxxxxx>
Message-ID: <YGDqGB/tmAa2cjOz@xxxxxxxxxxxxxxx>
Content-Disposition: inline
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
commit 97181f9bd57405b879403763284537e27d46963d upstream.
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@xxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/futex.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3018,8 +3018,10 @@ 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:
Patches currently in stable-queue which might be from ben@xxxxxxxxxxxxxxx are
queue-4.9/futex-drop-hb-lock-before-enqueueing-on-the-rtmutex.patch
queue-4.9/futex-rework-futex_lock_pi-to-use-rt_mutex_-_proxy_lock.patch
queue-4.9/futex-avoid-freeing-an-active-timer.patch
queue-4.9/futex-rt_mutex-introduce-rt_mutex_init_waiter.patch
queue-4.9/futex-fix-incorrect-should_fail_futex-handling.patch
queue-4.9/futex-rt_mutex-fix-rt_mutex_cleanup_proxy_lock.patch
queue-4.9/futex-use-smp_store_release-in-mark_wake_futex.patch
queue-4.9/futex-fix-possible-missed-wakeup.patch
queue-4.9/locking-futex-allow-low-level-atomic-operations-to-return-eagain.patch
queue-4.9/futex-prevent-robust-futex-exit-race.patch
queue-4.9/futex-handle-transient-ownerless-rtmutex-state-correctly.patch
queue-4.9/futex-handle-early-deadlock-return-correctly.patch
queue-4.9/arm64-futex-bound-number-of-ldxr-stxr-loops-in-futex_wake_op.patch
