The patch titled
posix-timers: fix deletion race
has been added to the -mm tree. Its filename is
posix-timers-fix-deletion-race.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: posix-timers: fix deletion race
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
timer_delete does:
lock_timer();
timer->it_process = NULL;
unlock_timer();
release_posix_timer();
timer->it_process is checked in lock_timer() to prevent access to a
timer, which is on the way to be deleted, but the check happens after
idr_lock is dropped. This allows release_posix_timer() to delete the
timer before the lock code can check the timer:
CPU 0 CPU 1
lock_timer();
timer->it_process = NULL;
unlock_timer();
lock_timer()
spin_lock(idr_lock);
timer = idr_find();
spin_lock(timer->lock);
spin_unlock(idr_lock);
release_posix_timer();
spin_lock(idr_lock);
idr_remove(timer);
spin_unlock(idr_lock);
free_timer(timer);
if (timer->......)
Change the locking to prevent this.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/posix-timers.c | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)
diff -puN kernel/posix-timers.c~posix-timers-fix-deletion-race kernel/posix-timers.c
--- a/kernel/posix-timers.c~posix-timers-fix-deletion-race
+++ a/kernel/posix-timers.c
@@ -605,13 +605,14 @@ static struct k_itimer * lock_timer(time
timr = (struct k_itimer *) idr_find(&posix_timers_id, (int) timer_id);
if (timr) {
spin_lock(&timr->it_lock);
- spin_unlock(&idr_lock);
if ((timr->it_id != timer_id) || !(timr->it_process) ||
timr->it_process->tgid != current->tgid) {
- unlock_timer(timr, *flags);
+ spin_unlock(&timr->it_lock);
+ spin_unlock_irqrestore(&idr_lock, *flags);
timr = NULL;
- }
+ } else
+ spin_unlock(&idr_lock);
} else
spin_unlock_irqrestore(&idr_lock, *flags);
_
Patches currently in -mm which might be from tglx@xxxxxxxxxxxxx are
futex_unlock_pi-hurts-my-brain-and-may-cause.patch
posix-timers-fix-deletion-race.patch
posix-timers-fix-creation-race.patch
signalfd-fix-interaction-with-posix-timers.patch
signalfd-make-it-group-wide-fix-posix-timers-scheduling.patch
git-acpi.patch
geode-mfgpt-support-for-geode-class-machines.patch
geode-mfgpt-clock-event-device-support.patch
nohz-fix-nohz-x86-dyntick-idle-handling.patch
x86_64-hpet-restore-vread.patch
x86_64-restore-restore-nohpet-cmdline.patch
x86_64-prep-idle-loop-for-dynticks.patch
x86_64-enable-high-resolution-timers-and-dynticks.patch
x86_64-dynticks-disable-hpet_id_legsup-hpets.patch
time-simplify-smp_call_function_single-call-sequence.patch
kernel-rtmutex-debugc-cleanups.patch
kernel-time-clocksourcec-use-list_for_each_entry-instead-of-list_for_each.patch
whitespace-fixes-time-syscalls.patch
whitespace-fixes-interval-timers.patch
whitespace-fixes-system-timers.patch
-
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