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Message-ID: <bd81a9a2-f14f-9564-3f68-be853134ecba@meizu.com>
Date:   Tue, 31 May 2022 09:37:12 +0800
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Subject: Re: [PATCH] drm/msm/dpu: Fix pointer dereferenced before checking
To:     Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Rob Clark <robdclark@gmail.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        "Sean Paul" <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>
CC:     <linux-arm-msm@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
        <freedreno@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>
References: <1653896005-25168-1-git-send-email-baihaowen@meizu.com>
 <68443e94-32fc-a35e-3383-0dcd8ca967c0@quicinc.com>
From:   baihaowen <baihaowen@meizu.com>
In-Reply-To: <68443e94-32fc-a35e-3383-0dcd8ca967c0@quicinc.com>
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在 2022/5/31 上午8:36, Abhinav Kumar 写道:
>
>
> On 5/30/2022 12:33 AM, Haowen Bai wrote:
>> The ctx->hw is dereferencing before null checking, so move
>> it after checking.
>>
>> Signed-off-by: Haowen Bai <baihaowen@meizu.com>
>
> Agree with Dmitry's comment. Adjust the patch subject to a different one otherwise PW thinks they are same patches.
>
> Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.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