[PATCH net-next] ptp: validate the requested frequency adjustment.

[PATCH net-next] ptp: validate the requested frequency adjustment.

[Richard Cochran]

PTP Hardware Clock drivers specify a maximum frequency adjustment that
their clocks can accommodate. Normally, user space programs will want to
respect the advertised limits. However, no kernel or driver code checks
that the dialed frequency offset is within the bounds, and out of range
values can lead to surprising results.

This patch fixes the issue by rejecting bad values.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
---
 drivers/ptp/ptp_clock.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index e25d2bc..296b0ec 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -142,7 +142,10 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct timex *tx)
 		delta = ktime_to_ns(kt);
 		err = ops->adjtime(ops, delta);
 	} else if (tx->modes & ADJ_FREQUENCY) {
-		err = ops->adjfreq(ops, scaled_ppm_to_ppb(tx->freq));
+		s32 ppb = scaled_ppm_to_ppb(tx->freq);
+		if (ppb > ops->max_adj || ppb < -ops->max_adj)
+			return -ERANGE;
+		err = ops->adjfreq(ops, ppb);
 		ptp->dialed_frequency = tx->freq;
 	} else if (tx->modes == 0) {
 		tx->freq = ptp->dialed_frequency;
-- 
1.7.10.4

Re: [PATCH net-next] ptp: validate the requested frequency adjustment.

[David Miller]

From: Richard Cochran <richardcochran@gmail.com>
Date: Sun, 27 Apr 2014 15:01:27 +0200

> PTP Hardware Clock drivers specify a maximum frequency adjustment that
> their clocks can accommodate. Normally, user space programs will want to
> respect the advertised limits. However, no kernel or driver code checks
> that the dialed frequency offset is within the bounds, and out of range
> values can lead to surprising results.
> 
> This patch fixes the issue by rejecting bad values.
> 
> Signed-off-by: Richard Cochran <richardcochran@gmail.com>

Applied.