[PATCH] drm: zynqmp_dp: Fix integer overflow in zynqmp_dp_rate_get()

[PATCH] drm: zynqmp_dp: Fix integer overflow in zynqmp_dp_rate_get()

[Karol Przybylski]

This patch fixes a potential integer overflow in the zynqmp_dp_rate_get() function.

The issue comes up when the expression drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000 is evaluated using 32-bit arithmetic.

Now the constant is casted to compatible u64 type.

Resolves CID 1636340 and CID 1635811

Signed-off-by: Karol Przybylski <karprzy7@gmail.com>
---
 drivers/gpu/drm/xlnx/zynqmp_dp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index 25c5dc61e..55e92344b 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -2190,7 +2190,7 @@ static int zynqmp_dp_rate_get(void *data, u64 *val)
 	struct zynqmp_dp *dp = data;
 
 	mutex_lock(&dp->lock);
-	*val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000;
+	*val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * (u64)10000;
 	mutex_unlock(&dp->lock);
 	return 0;
 }
-- 
2.34.1

Re: [PATCH] drm: zynqmp_dp: Fix integer overflow in zynqmp_dp_rate_get()

[Laurent Pinchart]

Hi Karol,

Thank you for the patch.

On Wed, Dec 11, 2024 at 01:20:26PM +0100, Karol Przybylski wrote:
> This patch fixes a potential integer overflow in the zynqmp_dp_rate_get() function.
> 
> The issue comes up when the expression drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000 is evaluated using 32-bit arithmetic.

Please wrap your commit message text to 82 columns.

> 
> Now the constant is casted to compatible u64 type.
> 
> Resolves CID 1636340 and CID 1635811
> 

Does this need a Fixes: tag ? How about 'Cc: stable@vger.kernel.org' to
get it backported to stable kernels ?

> Signed-off-by: Karol Przybylski <karprzy7@gmail.com>
> ---
>  drivers/gpu/drm/xlnx/zynqmp_dp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> index 25c5dc61e..55e92344b 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> @@ -2190,7 +2190,7 @@ static int zynqmp_dp_rate_get(void *data, u64 *val)
>  	struct zynqmp_dp *dp = data;
>  
>  	mutex_lock(&dp->lock);
> -	*val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000;
> +	*val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * (u64)10000;

You can also make the integer a 64-bit constant with

	*val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000ULL;

>  	mutex_unlock(&dp->lock);
>  	return 0;
>  }

-- 
Regards,

Laurent Pinchart

Re: [PATCH] drm: zynqmp_dp: Fix integer overflow in zynqmp_dp_rate_get()

[Karol P]

On Wed, 11 Dec 2024 at 13:59, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Karol,
>
> Thank you for the patch.
>
> On Wed, Dec 11, 2024 at 01:20:26PM +0100, Karol Przybylski wrote:
> > This patch fixes a potential integer overflow in the zynqmp_dp_rate_get() function.
> >
> > The issue comes up when the expression drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000 is evaluated using 32-bit arithmetic.
>
> Please wrap your commit message text to 82 columns.
>
> >
> > Now the constant is casted to compatible u64 type.
> >
> > Resolves CID 1636340 and CID 1635811
> >
>
> Does this need a Fixes: tag ? How about 'Cc: stable@vger.kernel.org' to
> get it backported to stable kernels ?

Thanks for the feedback, I'll add it.

>
> > Signed-off-by: Karol Przybylski <karprzy7@gmail.com>
> > ---
> >  drivers/gpu/drm/xlnx/zynqmp_dp.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > index 25c5dc61e..55e92344b 100644
> > --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > @@ -2190,7 +2190,7 @@ static int zynqmp_dp_rate_get(void *data, u64 *val)
> >       struct zynqmp_dp *dp = data;
> >
> >       mutex_lock(&dp->lock);
> > -     *val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000;
> > +     *val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * (u64)10000;
>
> You can also make the integer a 64-bit constant with
>
>         *val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000ULL;
>
> >       mutex_unlock(&dp->lock);
> >       return 0;
> >  }

It does look better. I will send v2 of this patch.

>
> --
> Regards,
>
> Laurent Pinchart