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@gmail.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
index ec784e58da5c1cd612059c5f80daea4316410309..414e585ec7dd0b0561f338da1b24f623fe4462b0 100644 (file)
--- 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);