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ntp: Verify offset doesn't overflow in ntp_update_offset

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We need to make sure that the offset is valid before manipulating it,
otherwise it might overflow on the multiplication.

Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
[jstultz: Reworked one of the checks so it makes more sense]
Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
Sasha Levin 2015-12-03 15:46:48 -05:00 committed by John Stultz
parent 3b44edaaa1
commit 52d189f1b3
1 changed files with 5 additions and 3 deletions
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8
kernel/time/ntp.c
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@ -297,15 +297,17 @@ static void ntp_update_offset(long offset)
if (!(time_status & STA_PLL)) if (!(time_status & STA_PLL))
return; return;
if (!(time_status & STA_NANO)) if (!(time_status & STA_NANO)) {
/* Make sure the multiplication below won't overflow */
offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
offset *= NSEC_PER_USEC; offset *= NSEC_PER_USEC;
}
/* /*
* Scale the phase adjustment and * Scale the phase adjustment and
* clamp to the operating range. * clamp to the operating range.
*/ */
offset = min(offset, MAXPHASE); offset = clamp(offset, -MAXPHASE, MAXPHASE);
offset = max(offset, -MAXPHASE);
/* /*
* Select how the frequency is to be controlled * Select how the frequency is to be controlled