linux-kernel - [PATCH] drm/vkms: fix variable dereferenced before check warning

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Date:   Thu,  8 Sep 2022 03:56:23 -0700
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     harshit.m.mogalapalli@...cle.com, dan.carpenter@...cle.com,
        Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
        Melissa Wen <melissa.srw@...il.com>,
        Haneen Mohammed <hamohammed.sa@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Igor Torrente <igormtorrente@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/vkms: fix variable dereferenced before check warning

Smatch warns:

drivers/gpu/drm/vkms/vkms_plane.c:110 vkms_plane_atomic_update() warn:
 variable dereferenced before check 'fb' (see line 108)

Fix the warning by moving the dereference after the NULL check.

Fixes: 8ba1648567e2 ("drm: vkms: Refactor the plane composer to accept new formats")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
---
 drivers/gpu/drm/vkms/vkms_plane.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
index f4319066adcc..c3a845220e10 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -105,11 +105,12 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
 	struct drm_shadow_plane_state *shadow_plane_state;
 	struct drm_framebuffer *fb = new_state->fb;
 	struct vkms_frame_info *frame_info;
-	u32 fmt = fb->format->format;
+	u32 fmt;
 
 	if (!new_state->crtc || !fb)
 		return;
 
+	fmt = fb->format->format;
 	vkms_plane_state = to_vkms_plane_state(new_state);
 	shadow_plane_state = &vkms_plane_state->base;
 
-- 
2.31.1