diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2024-10-01 10:42:00 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-10-29 11:43:18 +0100 |
| commit | 68f99be287a59d50a9ad231d523f7e578f8bd28a (patch) | |
| tree | ccd6b69aa68725390557779e19ea1fbad12dd212 /kernel/time | |
| parent | 92b043fd995a63a57aae29ff85a39b6f30cd440c (diff) | |
signal: Confine POSIX_TIMERS properly
Move the itimer rearming out of the signal code and consolidate all posix
timer related functions in the signal code under one ifdef.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241001083835.314100569@linutronix.de
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/itimer.c | 22 | ||||
| -rw-r--r-- | kernel/time/posix-timers.c | 15 |
2 files changed, 34 insertions, 3 deletions
diff --git a/kernel/time/itimer.c b/kernel/time/itimer.c index 00629e658ca1..876d389b2e21 100644 --- a/kernel/time/itimer.c +++ b/kernel/time/itimer.c @@ -151,7 +151,27 @@ COMPAT_SYSCALL_DEFINE2(getitimer, int, which, #endif /* - * The timer is automagically restarted, when interval != 0 + * Invoked from dequeue_signal() when SIG_ALRM is delivered. + * + * Restart the ITIMER_REAL timer if it is armed as periodic timer. Doing + * this in the signal delivery path instead of self rearming prevents a DoS + * with small increments in the high reolution timer case and reduces timer + * noise in general. + */ +void posixtimer_rearm_itimer(struct task_struct *tsk) +{ + struct hrtimer *tmr = &tsk->signal->real_timer; + + if (!hrtimer_is_queued(tmr) && tsk->signal->it_real_incr != 0) { + hrtimer_forward(tmr, tmr->base->get_time(), + tsk->signal->it_real_incr); + hrtimer_restart(tmr); + } +} + +/* + * Interval timers are restarted in the signal delivery path. See + * posixtimer_rearm_itimer(). */ enum hrtimer_restart it_real_fn(struct hrtimer *timer) { diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index fc40dacabe78..d461a32b7260 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -251,7 +251,7 @@ static void common_hrtimer_rearm(struct k_itimer *timr) /* * This function is called from the signal delivery code if - * info->si_sys_private is not zero, which indicates that the timer has to + * info::si_sys_private is not zero, which indicates that the timer has to * be rearmed. Restart the timer and update info::si_overrun. */ void posixtimer_rearm(struct kernel_siginfo *info) @@ -259,9 +259,15 @@ void posixtimer_rearm(struct kernel_siginfo *info) struct k_itimer *timr; unsigned long flags; + /* + * Release siglock to ensure proper locking order versus + * timr::it_lock. Keep interrupts disabled. + */ + spin_unlock(¤t->sighand->siglock); + timr = lock_timer(info->si_tid, &flags); if (!timr) - return; + goto out; if (timr->it_interval && timr->it_requeue_pending == info->si_sys_private) { timr->kclock->timer_rearm(timr); @@ -275,6 +281,11 @@ void posixtimer_rearm(struct kernel_siginfo *info) } unlock_timer(timr, flags); +out: + spin_lock(¤t->sighand->siglock); + + /* Don't expose the si_sys_private value to userspace */ + info->si_sys_private = 0; } int posix_timer_queue_signal(struct k_itimer *timr) |