> -----Original Message-----
> From: Tuo Li <isli...@gmail.com>
> Sent: Friday, June 30, 2023 11:19 AM
> To: inki....@samsung.com; sw0312....@samsung.com;
> kyungmin.p...@samsung.com; airl...@gmail.com; dan...@ffwll.ch;
> krzysztof.kozlow...@linaro.org; alim.akh...@samsung.com
> Cc: dri-devel@lists.freedesktop.org; linux-arm-ker...@lists.infradead.org;
> linux-samsung-...@vger.kernel.org; linux-ker...@vger.kernel.org;
> baijiaju1...@outlook.com; Tuo Li <isli...@gmail.com>; BassCheck
> <b...@buaa.edu.cn>
> Subject: [PATCH] drm/exynos: fix a possible null-pointer dereference due
> to data race in exynos_drm_crtc_atomic_disable()
>
> 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 <b...@buaa.edu.cn>
> Signed-off-by: Tuo Li <isli...@gmail.com>
Applied.
Thanks,
Inki Dae
> ---
> drivers/gpu/drm/exynos/exynos_drm_crtc.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> index 4153f302de7c..d19e796c2061 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
> @@ -39,13 +39,12 @@ static void exynos_drm_crtc_atomic_disable(struct
> drm_crtc *crtc,
> if (exynos_crtc->ops->atomic_disable)
> exynos_crtc->ops->atomic_disable(exynos_crtc);
>
> + spin_lock_irq(&crtc->dev->event_lock);
> if (crtc->state->event && !crtc->state->active) {
> - spin_lock_irq(&crtc->dev->event_lock);
> drm_crtc_send_vblank_event(crtc, crtc->state->event);
> - spin_unlock_irq(&crtc->dev->event_lock);
> -
> crtc->state->event = NULL;
> }
> + spin_unlock_irq(&crtc->dev->event_lock);
> }
>
> static int exynos_crtc_atomic_check(struct drm_crtc *crtc,
> --
> 2.34.1
