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Subject[017/102] rtc: limit frequency
3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Thomas Gleixner <tglx@linutronix.de>

commit 431e2bcc371016824f419baa745f82388258f3ee upstream.

Due to the hrtimer self rearming mode a user can DoS the machine simply
because it's starved by hrtimer events.

The RTC hrtimer is self rearming. We really need to limit the frequency
to something sensible.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ben Greear <greearb@candelatech.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/rtc/interface.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -708,7 +708,7 @@ int rtc_irq_set_freq(struct rtc_device *
int err = 0;
unsigned long flags;

- if (freq <= 0)
+ if (freq <= 0 || freq > 5000)
return -EINVAL;
retry:
spin_lock_irqsave(&rtc->irq_task_lock, flags);



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