[PATCH] gpu-drm-tiny-cirrus: Add NULL check of pointer pipe->plane.state->fb in cirrus_pipe_update()

[Alexander Sapozhnikov <alsp705@gmail.com>]

From: Alexandr Sapozhnikov <alsp705@gmail.com>

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.

Signed-off-by: Alexandr Sapozhnikov <alsp705@gmail.com>
---
 drivers/gpu/drm/tiny/cirrus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
index 678c2ef..ffa7e61 100644
--- a/drivers/gpu/drm/tiny/cirrus.c
+++ b/drivers/gpu/drm/tiny/cirrus.c
@@ -455,7 +455,7 @@ 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);
 }
 
-- 
2.5.3