drm/fb_dma: Add checks in drm_fb_dma_get_scanout_buffer()

plane->state and plane->state->fb can be NULL, so add a check before
dereferencing them.
Found by testing with the imx driver.

Fixes: 879b3b6511fe ("drm/fb_dma: Add generic get_scanout_buffer() for drm_panic")
Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240426121121.241366-1-jfalempe@redhat.com
(cherry picked from commit 986c12d8c9a677c094c37bd6aa636b4d4c5ccd46)
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

diff --git a/drivers/gpu/drm/drm_fb_dma_helper.c b/drivers/gpu/drm/drm_fb_dma_helper.c
index 96e5ab960f12933195cd0729ba9fc3af112b9134..e1d61a65210b07f386ab65369da7868a0fca735a 100644 (file)
--- a/drivers/gpu/drm/drm_fb_dma_helper.c
+++ b/drivers/gpu/drm/drm_fb_dma_helper.c
@@ -167,6 +167,9 @@ int drm_fb_dma_get_scanout_buffer(struct drm_plane *plane,
        struct drm_gem_dma_object *dma_obj;
        struct drm_framebuffer *fb;
 
+       if (!plane->state || !plane->state->fb)
+               return -EINVAL;
+
        fb = plane->state->fb;
        /* Only support linear modifier */
        if (fb->modifier != DRM_FORMAT_MOD_LINEAR)