From: Rob Clark <robdclark@chromium.org> stable inclusion from stable-v4.19.270 commit 19ec87d06acfab2313ee82b2a689bf0c154e57ea category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IALIA1 CVE: CVE-2022-48899 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ 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-robdcl... Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Zeng Heng <zengheng4@huawei.com> --- drivers/gpu/drm/virtio/virtgpu_ioctl.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c index 8d2f5ded86d6..a539843a03ba 100644 --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c @@ -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) { -- 2.25.1