drm/cirrus: NULL-check pipe->plane.state->fb in cirrus_pipe_update()

[ Upstream commit 7245e629dcaaf308f1868aeffa218e9849c77893 ]

After having been compared to NULL value at cirrus.c:455, pointer
'pipe->plane.state->fb' is passed as 1st parameter in call to function
'cirrus_fb_blit_rect' at cirrus.c:461, where it is dereferenced at
cirrus.c:316.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

v2:
	* aligned commit message to line-length limits

Signed-off-by: Alexandr Sapozhnikov <alsp705@gmail.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230215171549.16305-1-alsp705@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
index 4611ec408506ba16a4e49f06cad37682a7732d0a..2a81311b2217292aea0da836d0f64168773a36ed 100644 (file)
--- a/drivers/gpu/drm/tiny/cirrus.c
+++ b/drivers/gpu/drm/tiny/cirrus.c
@@ -450,7 +450,7 @@ static void cirrus_pipe_update(struct drm_simple_display_pipe *pipe,
        if (state->fb && cirrus->cpp != cirrus_cpp(state->fb))
                cirrus_mode_set(cirrus, &crtc->mode, state->fb);
 
-       if (drm_atomic_helper_damage_merged(old_state, state, &rect))
+       if (state->fb && drm_atomic_helper_damage_merged(old_state, state, &rect))
                cirrus_fb_blit_rect(state->fb, &shadow_plane_state->data[0], &rect);
 }