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

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Message-Id: <20220628005204.838739-1-sunliming@kylinos.cn>
Date:   Tue, 28 Jun 2022 08:52:04 +0800
From:   sunliming <sunliming@...inos.cn>
To:     quic_abhinavk@...cinc.com, robdclark@...il.com,
        dmitry.baryshkov@...aro.org
Cc:     linux-kernel@...r.kernel.org, freedreno@...ts.freedesktop.org,
        dan.carpenter@...cle.com, kelulanainsley@...il.com,
        sunliming@...inos.cn, kernel test robot <lkp@...el.com>
Subject: [PATCH RESEND] drm/msm/dpu: Fix variable dereferenced before check

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'

Fixes: d7d0e73f7de3 ("drm/msm/dpu: introduce the dpu_encoder_phys_* for writeback")
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: sunliming <sunliming@...inos.cn>
Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 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);
 
-- 
2.25.1