linux-kernel - Re: [PATCH] drm/msm/dpu: Fix pointer dereferenced before checking

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Message-ID: <7dd43198-2873-8767-2b17-de0b858a0ff1@meizu.com>
Date:   Tue, 31 May 2022 09:34:07 +0800
From:   baihaowen <baihaowen@...zu.com>
To:     Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
CC:     <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/dpu: Fix pointer dereferenced before checking

在 2022/5/30 下午3:33, Haowen Bai 写道:
> The ctx->hw is dereferencing before null checking, so move
> it after checking.
>
> Signed-off-by: Haowen Bai <baihaowen@...zu.com>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.c
> index bcccce292937..e59680cdd0ce 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.c
> @@ -155,11 +155,13 @@ static void dpu_hw_wb_roi(struct dpu_hw_wb *ctx, struct dpu_hw_wb_cfg *wb)
>  static void dpu_hw_wb_setup_qos_lut(struct dpu_hw_wb *ctx,
>  		struct dpu_hw_wb_qos_cfg *cfg)
>  {
> -	struct dpu_hw_blk_reg_map *c = &ctx->hw;
> +	struct dpu_hw_blk_reg_map *c;
>  	u32 qos_ctrl = 0;
>  
>  	if (!ctx || !cfg)
>  		return;
> +	
> +	c = &ctx->hw;
>  
>  	DPU_REG_WRITE(c, WB_DANGER_LUT, cfg->danger_lut);
>  	DPU_REG_WRITE(c, WB_SAFE_LUT, cfg->safe_lut);
Sorry, plz ignore this patch.

ctx->hw is dereferenced, &ctx->hw is just a pointer math for pointer address offset, so it would not cause a bug(dereferencing null pointer).

 

-- 
Haowen Bai