2019-08-12 00:08:58

by Gustavo A. R. Silva

Subject: [PATCH] drm/komeda: Fix potential integer overflow in komeda_crtc_update_clock_ratio

Add suffix ULL to constant 1000 in order to avoid a potential integer
overflow and give the compiler complete information about the proper
arithmetic to use. Notice that this constant is being used in a context
that expects an expression of type u64, but it's currently evaluated
using 32-bit arithmetic.

Addresses-Coverity-ID: 1485796 ("Unintentional integer overflow")
Fixes: ed22c6d9304d ("drm/komeda: Use drm_display_mode "crtc_" prefixed hardware timings")
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
index fa9a4593bb37..624d257da20f 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
@@ -27,7 +27,7 @@ static void komeda_crtc_update_clock_ratio(struct komeda_crtc_state *kcrtc_st)
return;
}

- pxlclk = kcrtc_st->base.adjusted_mode.crtc_clock * 1000;
+ pxlclk = kcrtc_st->base.adjusted_mode.crtc_clock * 1000ULL;
aclk = komeda_crtc_get_aclk(kcrtc_st);

kcrtc_st->clock_ratio = div64_u64(aclk << 32, pxlclk);
--
2.22.0

2019-08-12 10:21:50

by James Qian Wang

Subject: Re: drm/komeda: Fix potential integer overflow in komeda_crtc_update_clock_ratio

On Sun, Aug 11, 2019 at 07:08:01PM -0500, Gustavo A. R. Silva wrote:
> Add suffix ULL to constant 1000 in order to avoid a potential integer
> overflow and give the compiler complete information about the proper
> arithmetic to use. Notice that this constant is being used in a context
> that expects an expression of type u64, but it's currently evaluated
> using 32-bit arithmetic.
>
> Addresses-Coverity-ID: 1485796 ("Unintentional integer overflow")
> Fixes: ed22c6d9304d ("drm/komeda: Use drm_display_mode "crtc_" prefixed hardware timings")
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> index fa9a4593bb37..624d257da20f 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> @@ -27,7 +27,7 @@ static void komeda_crtc_update_clock_ratio(struct komeda_crtc_state *kcrtc_st)
> return;
> }
>
> - pxlclk = kcrtc_st->base.adjusted_mode.crtc_clock * 1000;
> + pxlclk = kcrtc_st->base.adjusted_mode.crtc_clock * 1000ULL;
> aclk = komeda_crtc_get_aclk(kcrtc_st);
>
> kcrtc_st->clock_ratio = div64_u64(aclk << 32, pxlclk);

Thank you for the patch.

Reviewed-by: James Qian Wang (Arm Technology China) <[email protected]>