In `dt3k_ns_to_timer()` the following lines near the end of the function
result in a signed integer overflow:
prescale = 15;
base = timer_base * (1 << prescale);
divider = 65535;
*nanosec = divider * base;
(`divider`, `base` and `prescale` are type `int`, `timer_base` and
`*nanosec` are type `unsigned int`. The value of `timer_base` will be
either 50 or 100.)
The main reason for the overflow is that the calculation for `base` is
completely wrong. It should be:
base = timer_base * (prescale + 1);
which matches an earlier instance of this calculation in the same
function.
Reported-by: David Binderman <dcb...@hotmail.com>
Cc: <sta...@vger.kernel.org>
Signed-off-by: Ian Abbott <abbo...@mev.co.uk>
---
N.B. Greg: The original report suggested an actual build error, so
may be prudent to queue this on your 'staging-linus' queue.
drivers/staging/comedi/drivers/dt3000.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/comedi/drivers/dt3000.c
b/drivers/staging/comedi/drivers/dt3000.c
index 2edf3ee91300..4ad176fc14ad 100644
--- a/drivers/staging/comedi/drivers/dt3000.c
+++ b/drivers/staging/comedi/drivers/dt3000.c
@@ -368,7 +368,7 @@ static int dt3k_ns_to_timer(unsigned int timer_base,
unsigned int *nanosec,
}
prescale = 15;
- base = timer_base * (1 << prescale);
+ base = timer_base * (prescale + 1);
divider = 65535;
*nanosec = divider * base;
return (prescale << 16) | (divider);
--
2.20.1
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