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SubjectRe: [PATCH] comedi: drivers: ni_tio: Fix arithmetic expression overflow
From
On 18/01/2024 09:32, Greg Kroah-Hartman wrote:
> On Thu, Jan 18, 2024 at 10:36:19AM +0300, Denis Arefev wrote:
>> The value of an arithmetic expression period_ns * 1000 is subject
>> to overflow due to a failure to cast operands to a larger data
>> type before performing arithmetic
>>
>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
>> Signed-off-by: Denis Arefev <arefev@swemel.ru>
>> ---
>> 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 da6826d77e60..acc914903c70 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 = period_ns * 1000UL;
>
> Can period_ns ever be "too big" to cause such an overflow?

The period_ns value comes from user-space and could be any unsigned int
value. It's used to let the driver know the period of an external clock
source.

> And what commit id does this fix?

Fixes: 3e90b1c7ebe9 ("staging: comedi: ni_tio: tidy up
ni_tio_set_clock_src() and helpers")
Cc: <stable@vger.kernel.org> # v5.15+

The first affected kernel version is v3.17. This patch should apply
cleanly to v5.13 onwards (when comedi was moved out of drivers/staging),
but earlier stable/longterm kernels would require a backported patch.

@Denis, if you could add the above Fixes: and Cc: lines to a v2 patch,
that would be great!

>
> thanks,
>
> greg k-h

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