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Message-Id: <20230908193656.3464052-1-sashal@kernel.org>
Date: Fri, 8 Sep 2023 15:36:53 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Tuo Li <islituo@...il.com>, BassCheck <bass@...a.edu.cn>,
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
Inki Dae <inki.dae@...sung.com>,
Sasha Levin <sashal@...nel.org>, sw0312.kim@...sung.com,
kyungmin.park@...sung.com, airlied@...il.com, daniel@...ll.ch,
dri-devel@...ts.freedesktop.org,
linux-arm-kernel@...ts.infradead.org,
linux-samsung-soc@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 1/3] drm/exynos: fix a possible null-pointer dereference due to data race in exynos_drm_crtc_atomic_disable()
From: Tuo Li <islituo@...il.com>
[ 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@...a.edu.cn>
Link: https://sites.google.com/view/basscheck/home
Signed-off-by: Tuo Li <islituo@...il.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Added relevant link.
Signed-off-by: Inki Dae <inki.dae@...sung.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
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 4787560bf93e7..e1aa518ea0ba1 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,
--
2.40.1
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