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drm/virtio: Fix GEM handle creation UAF

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[ Upstream commit 52531258318ed59a2dc5a43df2eaf0eb1d65438e ]

Userspace can guess the handle value and try to race GEM object creation
with handle close, resulting in a use-after-free if we dereference the
object after dropping the handle's reference.  For that reason, dropping
the handle's reference must be done *after* we are done dereferencing
the object.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Fixes: 62fb7a5e1096 ("virtio-gpu: add 3d/virgl support")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216233355.542197-2-robdclark@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Rob Clark 2022-12-16 15:33:55 -08:00 committed by Greg Kroah-Hartman
parent 34606ad218
commit 19ec87d06a
1 changed files with 9 additions and 1 deletions
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10
drivers/gpu/drm/virtio/virtgpu_ioctl.c
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@ -309,7 +309,6 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data,
}
return ret;
}
drm_gem_object_put_unlocked(obj);
rc->res_handle = res_id; /* similiar to a VM address */
rc->bo_handle = handle;
@ -318,6 +317,15 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data,
virtio_gpu_unref_list(&validate_list);
dma_fence_put(&fence->f);
}
/*
* The handle owns the reference now. But we must drop our
* remaining reference *after* we no longer need to dereference
* the obj. Otherwise userspace could guess the handle and
* race closing it from another thread.
*/
drm_gem_object_put_unlocked(obj);
return 0;
fail_unref:
if (vgdev->has_virgl_3d) {