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

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Message-ID: <bd81a9a2-f14f-9564-3f68-be853134ecba@meizu.com>
Date:   Tue, 31 May 2022 09:37:12 +0800
From:   baihaowen <baihaowen@...zu.com>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Rob Clark <robdclark@...il.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 2022/5/31 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@...zu.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@...cinc.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