This is a note to let you know that I've just added the patch titled
drm/exynos: fix a possible null-pointer dereference due to data race in exynos_drm_crtc_atomic_disable()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-exynos-fix-a-possible-null-pointer-dereference-d.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 982269200ab4860e888c0990f110b56997417f07
Author: Tuo Li <islituo@xxxxxxxxx>
Date: Fri Jun 30 10:19:06 2023 +0800
drm/exynos: fix a possible null-pointer dereference due to data race in exynos_drm_crtc_atomic_disable()
[ Upstream commit 2e63972a2de14482d0eae1a03a73e379f1c3f44c ]
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@xxxxxxxxxxx>
Link: https://sites.google.com/view/basscheck/home
Signed-off-by: Tuo Li <islituo@xxxxxxxxx>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
Added relevant link.
Signed-off-by: Inki Dae <inki.dae@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/exynos/exynos_drm_crtc.c b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
index 2696289ecc78f..b3e23ace5869c 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_crtc.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
@@ -43,13 +43,12 @@ static void exynos_drm_crtc_atomic_disable(struct drm_crtc *crtc,
if (exynos_crtc->ops->disable)
exynos_crtc->ops->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,
