diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2007-02-16 01:28:12 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-16 08:13:59 -0800 |
| commit | 8bfd9a7a229b5f3d3eda5d7d45c2eebec5b4ba16 (patch) | |
| tree | 01c910a659f387b921493cab9bd4decd8fa66a4e /kernel/signal.c | |
| parent | 54cdfdb47f73b5af3d1ebb0f1e383efbe70fde9e (diff) | |
[PATCH] hrtimers: prevent possible itimer DoS
Fix potential setitimer DoS with high-res timers by pushing itimer rearm
processing to process context.
[Fixes from: Ingo Molnar <mingo@elte.hu>]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/signal.c')
| -rw-r--r-- | kernel/signal.c | 58 |
1 files changed, 41 insertions, 17 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 8072e568bbe..e2a7d4bf7d5 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -456,26 +456,50 @@ static int __dequeue_signal(struct sigpending *pending, sigset_t *mask, 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_is_queued(tmr) && + tsk->signal->it_real_incr.tv64 != 0) { + hrtimer_forward(tmr, tmr->base->get_time(), + 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){ |