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Commit 52d189f1 authored by Sasha Levin's avatar Sasha Levin Committed by John Stultz
Browse files

ntp: Verify offset doesn't overflow in ntp_update_offset 



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: default avatarSasha Levin <sasha.levin@oracle.com>
[jstultz: Reworked one of the checks so it makes more sense]
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 3b44edaa

kernel/time/ntp.c

+5 −3
Original line number Diff line number Diff line
@@ -297,15 +297,17 @@ static void ntp_update_offset(long offset) 
	if (!(time_status & STA_PLL))

		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;

	}



	/*

	 * Scale the phase adjustment and

	 * clamp to the operating range.

	 */

	offset = min(offset, MAXPHASE);

	offset = max(offset, -MAXPHASE);

	offset = clamp(offset, -MAXPHASE, MAXPHASE);



	/*

	 * Select how the frequency is to be controlled