LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
* [PATCH] drm/msm/dsi: prevent unintentional integer overflow in dsi_pll_28nm_clk_recalc_rate()
@ 2021-09-29 17:51 Tim Gardner
  2021-10-01 22:44 ` Dmitry Baryshkov
  0 siblings, 1 reply; 2+ messages in thread
From: Tim Gardner @ 2021-09-29 17:51 UTC (permalink / raw)
  To: dri-devel
  Cc: tim.gardner, Rob Clark, Sean Paul, David Airlie, Daniel Vetter,
	Dmitry Baryshkov, Abhinav Kumar, linux-arm-msm, freedreno,
	linux-kernel

Coverity warns of an unintentional integer overflow

CID 120715 (#1 of 1): Unintentional integer overflow (OVERFLOW_BEFORE_WIDEN)
overflow_before_widen: Potentially overflowing expression ref_clk * sdm_byp_div
  with type unsigned int (32 bits, unsigned) is evaluated using 32-bit arithmetic,
  and then used in a context that expects an expression of type unsigned long
  (64 bits, unsigned).
To avoid overflow, cast either ref_clk or sdm_byp_div to type unsigned long.
263                vco_rate = ref_clk * sdm_byp_div;

Fix this and another possible overflow by casting ref_clk to unsigned long.

Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Abhinav Kumar <abhinavk@codeaurora.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: freedreno@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
index 2da673a2add6..cfe4b30eb96d 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
@@ -260,7 +260,7 @@ static unsigned long dsi_pll_28nm_clk_recalc_rate(struct clk_hw *hw,
 		sdm_byp_div = FIELD(
 				dsi_phy_read(base + REG_DSI_28nm_PHY_PLL_SDM_CFG0),
 				DSI_28nm_PHY_PLL_SDM_CFG0_BYP_DIV) + 1;
-		vco_rate = ref_clk * sdm_byp_div;
+		vco_rate = (unsigned long)ref_clk * sdm_byp_div;
 	} else {
 		/* sdm mode */
 		sdm_dc_off = FIELD(
@@ -274,7 +274,7 @@ static unsigned long dsi_pll_28nm_clk_recalc_rate(struct clk_hw *hw,
 		sdm_freq_seed = (sdm3 << 8) | sdm2;
 		DBG("sdm_freq_seed = %d", sdm_freq_seed);
 
-		vco_rate = (ref_clk * (sdm_dc_off + 1)) +
+		vco_rate = ((unsigned long)ref_clk * (sdm_dc_off + 1)) +
 			mult_frac(ref_clk, sdm_freq_seed, BIT(16));
 		DBG("vco rate = %lu", vco_rate);
 	}
-- 
2.33.0


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] drm/msm/dsi: prevent unintentional integer overflow in dsi_pll_28nm_clk_recalc_rate()
  2021-09-29 17:51 [PATCH] drm/msm/dsi: prevent unintentional integer overflow in dsi_pll_28nm_clk_recalc_rate() Tim Gardner
@ 2021-10-01 22:44 ` Dmitry Baryshkov
  0 siblings, 0 replies; 2+ messages in thread
From: Dmitry Baryshkov @ 2021-10-01 22:44 UTC (permalink / raw)
  To: Tim Gardner, dri-devel
  Cc: Rob Clark, Sean Paul, David Airlie, Daniel Vetter, Abhinav Kumar,
	linux-arm-msm, freedreno, linux-kernel

On 29/09/2021 20:51, Tim Gardner wrote:
> Coverity warns of an unintentional integer overflow
> 
> CID 120715 (#1 of 1): Unintentional integer overflow (OVERFLOW_BEFORE_WIDEN)
> overflow_before_widen: Potentially overflowing expression ref_clk * sdm_byp_div
>    with type unsigned int (32 bits, unsigned) is evaluated using 32-bit arithmetic,
>    and then used in a context that expects an expression of type unsigned long
>    (64 bits, unsigned).
> To avoid overflow, cast either ref_clk or sdm_byp_div to type unsigned long.
> 263                vco_rate = ref_clk * sdm_byp_div;
> 
> Fix this and another possible overflow by casting ref_clk to unsigned long.

Changing ref_clk from u32 to unsigned long would be a more simple and 
elegant way of fixing this issue. Could you please update your patch?

> 
> Cc: Rob Clark <robdclark@gmail.com>
> Cc: Sean Paul <sean@poorly.run>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> Cc: Abhinav Kumar <abhinavk@codeaurora.org>
> Cc: linux-arm-msm@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Cc: freedreno@lists.freedesktop.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
> ---
>   drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
> index 2da673a2add6..cfe4b30eb96d 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c
> @@ -260,7 +260,7 @@ static unsigned long dsi_pll_28nm_clk_recalc_rate(struct clk_hw *hw,
>   		sdm_byp_div = FIELD(
>   				dsi_phy_read(base + REG_DSI_28nm_PHY_PLL_SDM_CFG0),
>   				DSI_28nm_PHY_PLL_SDM_CFG0_BYP_DIV) + 1;
> -		vco_rate = ref_clk * sdm_byp_div;
> +		vco_rate = (unsigned long)ref_clk * sdm_byp_div;
>   	} else {
>   		/* sdm mode */
>   		sdm_dc_off = FIELD(
> @@ -274,7 +274,7 @@ static unsigned long dsi_pll_28nm_clk_recalc_rate(struct clk_hw *hw,
>   		sdm_freq_seed = (sdm3 << 8) | sdm2;
>   		DBG("sdm_freq_seed = %d", sdm_freq_seed);
>   
> -		vco_rate = (ref_clk * (sdm_dc_off + 1)) +
> +		vco_rate = ((unsigned long)ref_clk * (sdm_dc_off + 1)) +
>   			mult_frac(ref_clk, sdm_freq_seed, BIT(16));
>   		DBG("vco rate = %lu", vco_rate);
>   	}
> 


-- 
With best wishes
Dmitry

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2021-10-01 22:45 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-09-29 17:51 [PATCH] drm/msm/dsi: prevent unintentional integer overflow in dsi_pll_28nm_clk_recalc_rate() Tim Gardner
2021-10-01 22:44 ` Dmitry Baryshkov

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).