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Message-ID: <0b63ef49-7a59-0a72-503c-1de20a502c6a@linaro.org>
Date:   Mon, 9 Jan 2023 00:08:08 +0200
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Subject: Re: [PATCH] drm/msm/dpu: Add check for cstate
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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To:     Jiasheng Jiang <jiasheng@iscas.ac.cn>, robdclark@gmail.com,
        quic_abhinavk@quicinc.com, sean@poorly.run, airlied@gmail.com,
        daniel@ffwll.ch, quic_jesszhan@quicinc.com,
        ville.syrjala@linux.intel.com, yang.lee@linux.alibaba.com
Cc:     linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org
References: <20221206080517.43786-1-jiasheng@iscas.ac.cn>
 <e56c48c2-8439-c9c8-c735-95adece3c68d@linaro.org>
In-Reply-To: <e56c48c2-8439-c9c8-c735-95adece3c68d@linaro.org>
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On 08/01/2023 23:56, Dmitry Baryshkov wrote:
> On 06/12/2022 10:05, Jiasheng Jiang wrote:
>> As kzalloc may fail and return NULL pointer,
>> it should be better to check cstate
>> in order to avoid the NULL pointer dereference
>> in __drm_atomic_helper_crtc_reset.
>>
>> Fixes: 1cff7440a86e ("drm/msm: Convert to using 
>> __drm_atomic_helper_crtc_reset() for reset.")
>> Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> index 13ce321283ff..22c2787b7b38 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> @@ -968,7 +968,10 @@ static void dpu_crtc_reset(struct drm_crtc *crtc)
>>       if (crtc->state)
>>           dpu_crtc_destroy_state(crtc, crtc->state);
>> -    __drm_atomic_helper_crtc_reset(crtc, &cstate->base);
>> +    if (cstate)
>> +        __drm_atomic_helper_crtc_reset(crtc, &cstate->base);
>> +    else
>> +        __drm_atomic_helper_crtc_reset(crtc, NULL);
> 
> NAK.
> 
> The proper fix is to add the if() but to skip the else clause. We should 
> not reset the crtc's state if memory allocation failed.

On the other hand... Some of the drivers do exactly this ops.

With the message fixed:

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

-- 
With best wishes
Dmitry