linux-kernel - Re: [PATCH RESEND] drm/msm/dpu: Fix variable dereferenced before check

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Date:   Thu, 23 Jun 2022 10:32:51 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     sunliming <sunliming@...inos.cn>, <robdclark@...il.com>,
        <dmitry.baryshkov@...aro.org>
CC:     <linux-kernel@...r.kernel.org>, <kelulanainsley@...il.com>,
        <freedreno@...ts.freedesktop.org>,
        kernel test robot <lkp@...el.com>,
        "Dan Carpenter" <dan.carpenter@...cle.com>
Subject: Re: [PATCH RESEND] drm/msm/dpu: Fix variable dereferenced before
 check



On 6/22/2022 6:27 PM, sunliming wrote:
> Fixes the following smatch warning:
> 
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c:261
> dpu_encoder_phys_wb_atomic_check() warn: variable dereferenced before check 'conn_state'
> 
> Signed-off-by: sunliming <sunliming@...inos.cn>
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
Fixes: d7d0e73f7de3 ("drm/msm/dpu: introduce the dpu_encoder_phys_* for 
writeback")
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
> index 59da348ff339..0ec809ab06e7 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
> @@ -252,11 +252,6 @@ static int dpu_encoder_phys_wb_atomic_check(
>   	DPU_DEBUG("[atomic_check:%d, \"%s\",%d,%d]\n",
>   			phys_enc->wb_idx, mode->name, mode->hdisplay, mode->vdisplay);
>   
> -	if (!conn_state->writeback_job || !conn_state->writeback_job->fb)
> -		return 0;
> -
> -	fb = conn_state->writeback_job->fb;
> -
>   	if (!conn_state || !conn_state->connector) {
>   		DPU_ERROR("invalid connector state\n");
>   		return -EINVAL;
> @@ -267,6 +262,11 @@ static int dpu_encoder_phys_wb_atomic_check(
>   		return -EINVAL;
>   	}
>   
> +	if (!conn_state->writeback_job || !conn_state->writeback_job->fb)
> +		return 0;
> +
> +	fb = conn_state->writeback_job->fb;
> +
>   	DPU_DEBUG("[fb_id:%u][fb:%u,%u]\n", fb->base.id,
>   			fb->width, fb->height);
>