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Subject: Re: [PATCH] drm/exynos: gsc: Variable "gscblk_cfg" in function
 gsc_set_gscblk_fimd_wb() could be uninitialized
To:     Yizhuo <yzhai003@ucr.edu>
Cc:     csong@cs.ucr.edu, zhiyunq@cs.ucr.edu,
        Inki Dae <inki.dae@samsung.com>,
        Joonyoung Shim <jy0922.shim@samsung.com>,
        Seung-Woo Kim <sw0312.kim@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        David Airlie <airlied@linux.ie>, Kukjin Kim <kgene@kernel.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org
From:   Marek Szyprowski <m.szyprowski@samsung.com>
Message-ID: <455d9474-253d-7f1c-f312-08dffad242f3@samsung.com>
Date:   Tue, 29 Jan 2019 09:40:33 +0100
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        <20190128182851.8558-1-yzhai003@ucr.edu>
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Hi

On 2019-01-28 19:28, Yizhuo wrote:
> In function gsc_set_gscblk_fimd_wb(), local variable "gscblk_cfg"
> could be uninitialized of function regmap_read returns -EINVAL.
> However, this value will be  write to the register after "or"
> operation. This is potentially unsafe.
>
> Signed-off-by: Yizhuo <yzhai003@ucr.edu>
> ---
>  drivers/gpu/drm/exynos/exynos_drm_gsc.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_gsc.c b/drivers/gpu/drm/exynos/exynos_drm_gsc.c
> index 0506b2b17ac1..b1d0f974fe80 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_gsc.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_gsc.c
> @@ -441,11 +441,16 @@ static int gsc_sw_reset(struct gsc_context *ctx)
>  static void gsc_set_gscblk_fimd_wb(struct gsc_context *ctx, bool enable)

This function has been completely removed in mainline kernel by commit
8b7d3ec83aba ("drm/exynos: gsc: Convert driver to IPP v2 core API"), so
there is no need for any fix anymore.

>  {
>  	unsigned int gscblk_cfg;
> +	int ret;
>  
>  	if (!ctx->sysreg)
>  		return;
>  
> -	regmap_read(ctx->sysreg, SYSREG_GSCBLK_CFG1, &gscblk_cfg);
> +	ret = regmap_read(ctx->sysreg, SYSREG_GSCBLK_CFG1, &gscblk_cfg);
> +	if (ret) {
> +		DRM_ERROR("gsc: Fail to read system register\n");
> +		return;
> +	}
>  
>  	if (enable)
>  		gscblk_cfg |= GSC_BLK_DISP1WB_DEST(ctx->id) |

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland