rtc: limit frequency

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>

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 0900dfea3ae70d4c2dc455e1174c1b6e538fe7e3..3195dbd3ec3468910396c029e42d9613e206b283 100644 (file)
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -708,7 +708,7 @@ int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
        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);