Messages in this thread Patch in this message | | | From | John Stultz <> | Subject | [PATCH v2] ntp: Verify offset doesn't overflow in ntp_update_offset | Date | Thu, 10 Dec 2015 11:51:34 -0800 |
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From: Sasha Levin <sasha.levin@oracle.com>
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> --- v2: Reworked the overflow clamp to make more sense.
kernel/time/ntp.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index 149cc80..125fc03 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -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 -- 1.9.1
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