ptp: validate the requested frequency adjustment.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index e25d2bc898e5b6e4eb7b43e6df87129a2a19781e..296b0ec8744da915763f8444c2ae8e902376c33e 100644 (file)
--- 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;