do_div() does a 64-by-32 division. Here the divisor is an unsigned long
which on some platforms is 64 bit wide. So use div64_ul instead of do_div
to avoid a possible truncation. Issue identified using the
coccicheck tool.
Signed-off-by: Deepak R Varma <[email protected]>
---
Changes in v2:
1. No functional change.
Include outreachy mailing list on the to list
drivers/staging/iio/frequency/ad9834.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/staging/iio/frequency/ad9834.c b/drivers/staging/iio/frequency/ad9834.c
index 285df0e489a6..3917a76e7976 100644
--- a/drivers/staging/iio/frequency/ad9834.c
+++ b/drivers/staging/iio/frequency/ad9834.c
@@ -102,8 +102,7 @@ static unsigned int ad9834_calc_freqreg(unsigned long mclk, unsigned long fout)
{
unsigned long long freqreg = (u64)fout * (u64)BIT(AD9834_FREQ_BITS);
- do_div(freqreg, mclk);
- return freqreg;
+ return div64_ul(freqreg, mclk);
}
static int ad9834_write_frequency(struct ad9834_state *st,
--
2.34.1
> -----Original Message-----
> From: Deepak R Varma <[email protected]>
> Sent: Friday, October 28, 2022 12:00 AM
> To: [email protected]; Lars-Peter Clausen <[email protected]>;
> Hennerich, Michael <[email protected]>; Jonathan Cameron
> <[email protected]>; Greg Kroah-Hartman <[email protected]>;
> [email protected]; [email protected]; linux-
> [email protected]
> Subject: [PATCH v2] staging: iio: frequency: ad9834: Use div64_ul instead of
> do_div
>
> [External]
>
> do_div() does a 64-by-32 division. Here the divisor is an unsigned long
> which on some platforms is 64 bit wide. So use div64_ul instead of do_div
> to avoid a possible truncation. Issue identified using the
> coccicheck tool.
>
> Signed-off-by: Deepak R Varma <[email protected]>
> ---
Clearly, I should have looked better and only reply to this one:
Reviewed-by: Nuno S? <[email protected]>
On Fri, 28 Oct 2022 10:14:48 +0000
"Sa, Nuno" <[email protected]> wrote:
> > -----Original Message-----
> > From: Deepak R Varma <[email protected]>
> > Sent: Friday, October 28, 2022 12:00 AM
> > To: [email protected]; Lars-Peter Clausen <[email protected]>;
> > Hennerich, Michael <[email protected]>; Jonathan Cameron
> > <[email protected]>; Greg Kroah-Hartman <[email protected]>;
> > [email protected]; [email protected]; linux-
> > [email protected]
> > Subject: [PATCH v2] staging: iio: frequency: ad9834: Use div64_ul instead of
> > do_div
> >
> > [External]
> >
> > do_div() does a 64-by-32 division. Here the divisor is an unsigned long
> > which on some platforms is 64 bit wide. So use div64_ul instead of do_div
> > to avoid a possible truncation. Issue identified using the
> > coccicheck tool.
> >
> > Signed-off-by: Deepak R Varma <[email protected]>
> > ---
>
> Clearly, I should have looked better and only reply to this one:
>
> Reviewed-by: Nuno Sá <[email protected]>
As per the email Greg linked to, please take a close look at the surround code
and include analysis of whether the value can actually be greater than 32 bits.
Note that in most cases that would actually mean the code was broken on 32 bit
platforms.