The patch titled
high-res timers: do itimer rearming in process context
has been added to the -mm tree. Its filename is
updated-high-res-timers-core-high-res-timers-do-itimer-rearming-in-process-context.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: high-res timers: do itimer rearming in process context
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fix potential setitimer DoS with high-res timers by pushing itimer rearm
processing to process context.
[ mingo: i have tested this with an itimer stress-test that starts
short-timeout itimers from 1000 threads. ]
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/itimer.c | 5 ---
kernel/signal.c | 58 ++++++++++++++++++++++++++++++++--------------
2 files changed, 41 insertions(+), 22 deletions(-)
diff -puN kernel/itimer.c~updated-high-res-timers-core-high-res-timers-do-itimer-rearming-in-process-context kernel/itimer.c
--- a/kernel/itimer.c~updated-high-res-timers-core-high-res-timers-do-itimer-rearming-in-process-context
+++ a/kernel/itimer.c
@@ -135,11 +135,6 @@ enum hrtimer_restart it_real_fn(struct h
send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);
- if (sig->it_real_incr.tv64 != 0) {
- hrtimer_forward(timer, hrtimer_cb_get_time(timer),
- sig->it_real_incr);
- return HRTIMER_RESTART;
- }
return HRTIMER_NORESTART;
}
diff -puN kernel/signal.c~updated-high-res-timers-core-high-res-timers-do-itimer-rearming-in-process-context kernel/signal.c
--- a/kernel/signal.c~updated-high-res-timers-core-high-res-timers-do-itimer-rearming-in-process-context
+++ a/kernel/signal.c
@@ -456,26 +456,50 @@ static int __dequeue_signal(struct sigpe
int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
{
int signr = __dequeue_signal(&tsk->pending, mask, info);
- if (!signr)
+ if (!signr) {
signr = __dequeue_signal(&tsk->signal->shared_pending,
mask, info);
+ /*
+ * itimer signal ?
+ *
+ * itimers are process shared and we restart periodic
+ * itimers in the signal delivery path to prevent DoS
+ * attacks in the high resolution timer case. This is
+ * compliant with the old way of self restarting
+ * itimers, as the SIGALRM is a legacy signal and only
+ * queued once. Changing the restart behaviour to
+ * restart the timer in the signal dequeue path is
+ * reducing the timer noise on heavy loaded !highres
+ * systems too.
+ */
+ if (unlikely(signr == SIGALRM)) {
+ struct hrtimer *tmr = &tsk->signal->real_timer;
+
+ if (!hrtimer_active(tmr) &&
+ tsk->signal->it_real_incr.tv64 != 0) {
+ hrtimer_forward(tmr, hrtimer_cb_get_time(tmr),
+ tsk->signal->it_real_incr);
+ hrtimer_restart(tmr);
+ }
+ }
+ }
recalc_sigpending_tsk(tsk);
- if (signr && unlikely(sig_kernel_stop(signr))) {
- /*
- * Set a marker that we have dequeued a stop signal. Our
- * caller might release the siglock and then the pending
- * stop signal it is about to process is no longer in the
- * pending bitmasks, but must still be cleared by a SIGCONT
- * (and overruled by a SIGKILL). So those cases clear this
- * shared flag after we've set it. Note that this flag may
- * remain set after the signal we return is ignored or
- * handled. That doesn't matter because its only purpose
- * is to alert stop-signal processing code when another
- * processor has come along and cleared the flag.
- */
- if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT))
- tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
- }
+ if (signr && unlikely(sig_kernel_stop(signr))) {
+ /*
+ * Set a marker that we have dequeued a stop signal. Our
+ * caller might release the siglock and then the pending
+ * stop signal it is about to process is no longer in the
+ * pending bitmasks, but must still be cleared by a SIGCONT
+ * (and overruled by a SIGKILL). So those cases clear this
+ * shared flag after we've set it. Note that this flag may
+ * remain set after the signal we return is ignored or
+ * handled. That doesn't matter because its only purpose
+ * is to alert stop-signal processing code when another
+ * processor has come along and cleared the flag.
+ */
+ if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT))
+ tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
+ }
if ( signr &&
((info->si_code & __SI_MASK) == __SI_TIMER) &&
info->si_sys_private){
_
Patches currently in -mm which might be from tglx@xxxxxxxxxxxxx are
git-mtd.patch
ktime-fix-signed--unsigned-mismatch-in-ktime_to_ns.patch
gtod-exponential-update_wall_time.patch
gtod-persistent-clock-support-core.patch
gtod-persistent-clock-support-i386.patch
gtod-persistent-clock-support-i386-i386-unexport-read_persistent_clock.patch
time-uninline-jiffiesh.patch
time-uninline-jiffiesh-fix.patch
time-fix-msecs_to_jiffies-bug.patch
time-fix-timeout-overflow.patch
cleanup-uninline-irq_enter-and-move-it-into-a-function.patch
dynticks-extend-next_timer_interrupt-to-use-a-reference-jiffie.patch
dynticks-extend-next_timer_interrupt-to-use-a-reference-jiffie-remove-incorrect-warning-in-kernel-timerc.patch
hrtimers-namespace-and-enum-cleanup.patch
hrtimers-clean-up-locking.patch
updated-hrtimers-state-tracking.patch
updated-hrtimers-clean-up-callback-tracking.patch
updated-hrtimers-move-and-add-documentation.patch
updated-add-a-framework-to-manage-clock-event-devices.patch
updated-acpi-include-apich.patch
updated-acpi-keep-track-of-timer-broadcast.patch
updated-acpi-add-state-propagation-for-dynamic-broadcasting.patch
updated-i386-cleanup-apic-code.patch
updated-i386-convert-to-clock-event-devices.patch
updated-i386-convert-to-clock-event-devices-fix.patch
updated-i386-convert-to-clock-event-devices-arch-i386-kernel-apicc-make-a-function-static.patch
updated-i386-convert-to-clock-event-devices-remove-arch-i386-kernel-time_hpetchpet_reenable.patch
updated-pm_timer-allow-early-access-and-move-externs-to-a-header-file.patch
updated-i386-rework-local-apic-calibration.patch
updated-high-res-timers-core.patch
updated-high-res-timers-core-high-res-timers-do-itimer-rearming-in-process-context.patch
updated-gtod-mark-tsc-unusable-for-highres-timers.patch
high-res-timers-utilize-tsc-clocksource-again.patch
updated-dynticks-core-code.patch
updated-dyntick-add-nohz-stats-to-proc-stat.patch
updated-dynticks-i386-arch-code.patch
updated-dynticks-fix-nmi-watchdog.patch
updated-high-res-timers-dynticks-enable-i386-support.patch
updated-debugging-feature-timer-stats.patch
clockevents-core-check-for-clock-event-device-handler-being-non-null-before-calling-it.patch
round_jiffies-infrastructure.patch
round_jiffies-infrastructure-fix.patch
clocksource-add-usage-of-config_sysfs.patch
clocksource-small-cleanup-2.patch
clocksource-small-cleanup-2-fix.patch
clocksource-small-acpi_pm-cleanup.patch
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