linux-kernel - [PATCH 1/2] drm/virtio: fix virtio_gpu_execbuffer

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Date:   Tue, 11 Feb 2020 14:50:46 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     olvaffe@...il.com, gurchetansingh@...omium.org,
        Gerd Hoffmann <kraxel@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        virtualization@...ts.linux-foundation.org (open list:VIRTIO GPU DRIVER),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 1/2] drm/virtio: fix virtio_gpu_execbuffer_ioctl locking

Lockdep says we can't call vmemdup() while having objects reserved
because it needs the mmap semaphore.  So reorder the calls reserve
the objects later.

Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 205ec4abae2b..0477d1250f2d 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -126,22 +126,22 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 		bo_handles = NULL;
 	}
 
-	if (buflist) {
-		ret = virtio_gpu_array_lock_resv(buflist);
-		if (ret)
-			goto out_unused_fd;
-	}
-
 	buf = vmemdup_user(u64_to_user_ptr(exbuf->command), exbuf->size);
 	if (IS_ERR(buf)) {
 		ret = PTR_ERR(buf);
-		goto out_unresv;
+		goto out_unused_fd;
+	}
+
+	if (buflist) {
+		ret = virtio_gpu_array_lock_resv(buflist);
+		if (ret)
+			goto out_memdup;
 	}
 
 	out_fence = virtio_gpu_fence_alloc(vgdev);
 	if(!out_fence) {
 		ret = -ENOMEM;
-		goto out_memdup;
+		goto out_unresv;
 	}
 
 	if (out_fence_fd >= 0) {
@@ -160,11 +160,11 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 			      vfpriv->ctx_id, buflist, out_fence);
 	return 0;
 
-out_memdup:
-	kvfree(buf);
 out_unresv:
 	if (buflist)
 		virtio_gpu_array_unlock_resv(buflist);
+out_memdup:
+	kvfree(buf);
 out_unused_fd:
 	kvfree(bo_handles);
 	if (buflist)
-- 
2.18.2