[PATCH] drm/exynos: fix a possible null-pointer dereference due to data race in exynos_drm_crtc_atomic_disable()

[Krzysztof Kozlowski]

On 30/06/2023 04:19, Tuo Li wrote:
> The variable crtc->state->event is often protected by the lock 
> crtc->dev->event_lock when is accessed. However, it is accessed as a 
> condition of an if statement in exynos_drm_crtc_atomic_disable() without
> holding the lock:
> 
>   if (crtc->state->event && !crtc->state->active)
> 
> However, if crtc->state->event is changed to NULL by another thread right
> after the conditions of the if statement is checked to be true, a
> null-pointer dereference can occur in drm_crtc_send_vblank_event():
> 
>   e->pipe = pipe;
> 
> To fix this possible null-pointer dereference caused by data race, the 
> spin lock coverage is extended to protect the if statement as well as the 
> function call to drm_crtc_send_vblank_event().
> 
> Reported-by: BassCheck <bass at buaa.edu.cn>
> Signed-off-by: Tuo Li <islituo at gmail.com>

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski at linaro.org>

Best regards,
Krzysztof