commit: 431e2bcc371016824f419baa745f82388258f3ee
From: Thomas Gleixner <[email protected]>
Date: Tue, 26 Jul 2011 16:08:19 -0700
Subject: [PATCH] rtc: limit frequency

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 <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ben Greear <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
---
 drivers/rtc/interface.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index b6bf57f..601b053 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -688,7 +688,7 @@ 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;
 
        spin_lock_irqsave(&rtc->irq_task_lock, flags);

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