[PATCH 4/5] comedi: ni_tio: Fix overflow of the clock period

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Josef Bacik <josef@toxicpanda.com>

ni_tio_set_clock_src() stores the period of the clock source, which the
user passes in nanoseconds, in picoseconds:

	counter->clock_period_ps = period_ns * 1000;

period_ns is an unsigned int, so that the product is computed in 32
bits, although clock_period_ps is a u64. It wraps for periods above
4294967 ns, that is for external clocks slower than 233 Hz.
INSN_CONFIG_GET_CLOCK_SRC then reports a wrong period, and
ni_tio_set_sync_mode() decides on a wrong one: 4294968 ns become 704 ps,
which is below the limit of 25 ns under which the alternate
synchronization mode for fast clocks is switched on.

The multiplication was done in 64 bits until the constant
pico_per_nano, a uint64_t, was replaced by a literal. Widen again.

Fixes: 3e90b1c7ebe9 ("staging: comedi: ni_tio: tidy up ni_tio_set_clock_src() and helpers")
Cc: stable <stable@kernel.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/comedi/drivers/ni_tio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/comedi/drivers/ni_tio.c b/drivers/comedi/drivers/ni_tio.c
index c3a909abcfa7..b7ab70f34275 100644
--- a/drivers/comedi/drivers/ni_tio.c
+++ b/drivers/comedi/drivers/ni_tio.c
@@ -800,7 +800,7 @@ static int ni_tio_set_clock_src(struct ni_gpct *counter,
 				GI_PRESCALE_X2(counter_dev->variant) |
 				GI_PRESCALE_X8(counter_dev->variant), bits);
 	}
-	counter->clock_period_ps = period_ns * 1000;
+	counter->clock_period_ps = (u64)period_ns * 1000;
 	ni_tio_set_sync_mode(counter);
 	return 0;
 }

-- 
2.56.0