On Tue, Apr 23, 2019 at 04:53:53PM +0200, Noralf Trønnes wrote:
> Non-atomic drivers like ast doesn't have connector->state set resulting
> in a NULL pointer deref:
>
> [ 29.609593] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> [ 29.609619] Call Trace:
> [ 29.609630] ? drm_helper_probe_single_connector_modes+0x27f/0x680
> [ 29.609640] drm_setup_crtcs+0x431/0xd80 [drm_kms_helper]
> [ 29.753065] __drm_fb_helper_initial_config_and_unlock+0x6f/0x6a0
> [ 29.753160] ? drm_modeset_unlock_all+0x31/0x50 [drm]
> [ 29.765758] ast_fbdev_init+0xa8/0xc0 [ast]
> [ 29.765762] ast_driver_load.cold.7+0x2b3/0xe11 [ast]
> [ 29.765775] drm_dev_register+0x111/0x150 [drm]
>
> Fix by bailing out if the driver does not support atomic modesetting.
>
> Fixes: 09ded8af57bc ("drm/i915/fbdev: Move intel_fb_initial_config() to fbdev helper")
> Reported-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_fb_helper.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 2339f0f8f5a8..899c2eca26d1 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -2588,6 +2588,9 @@ static bool drm_fb_helper_firmware_config(struct drm_fb_helper *fb_helper,
> int num_connectors_detected = 0;
> struct drm_modeset_acquire_ctx ctx;
>
> + if (!drm_drv_uses_atomic_modeset(dev))
> + return false;
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
I think for merging we're already past feature freeze, but
drm-misc-next-fixes hasn't been rolled forward yet. I think you need to
wait for drm-misc maintainers to do that (I pinged them already), and then
put this one there.
-Daniel
> +
> save_enabled = kcalloc(count, sizeof(bool), GFP_KERNEL);
> if (!save_enabled)
> return false;
> --
> 2.20.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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