linux-kernel - [PATCH] drm/exynos: fix race condition UAF in exynos_g2d_exec

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Message-Id: <20230526130131.16521-1-lm0963hack@gmail.com>
Date:   Fri, 26 May 2023 21:01:31 +0800
From:   Min Li <lm0963hack@...il.com>
To:     inki.dae@...sung.com
Cc:     sw0312.kim@...sung.com, kyungmin.park@...sung.com,
        airlied@...il.com, daniel@...ll.ch, krzysztof.kozlowski@...aro.org,
        alim.akhtar@...sung.com, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/exynos: fix race condition UAF in exynos_g2d_exec_ioctl

If it is async, runqueue_node is freed in g2d_runqueue_worker on another
worker thread. So in extreme cases, if g2d_runqueue_worker runs first, and
then executes the following if statement, there will be use-after-free.

Signed-off-by: Min Li <lm0963hack@...il.com>
---
 drivers/gpu/drm/exynos/exynos_drm_g2d.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
index ec784e58da5c..414e585ec7dd 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
@@ -1335,7 +1335,7 @@ int exynos_g2d_exec_ioctl(struct drm_device *drm_dev, void *data,
 	/* Let the runqueue know that there is work to do. */
 	queue_work(g2d->g2d_workq, &g2d->runqueue_work);
 
-	if (runqueue_node->async)
+	if (req->async)
 		goto out;
 
 	wait_for_completion(&runqueue_node->complete);
-- 
2.34.1