The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Possible dependencies:
52531258318e ("drm/virtio: Fix GEM handle creation UAF") 897b4d1acaf5 ("drm/virtio: implement blob resources: resource create blob ioctl") 16845c5d5409 ("drm/virtio: implement blob resources: implement vram object") 6076a9711dc5 ("drm/virtio: implement blob resources: probe for host visible region") 6815cfe602d0 ("drm/virtio: implement blob resources: probe for the feature.") 30172efbfb84 ("drm/virtio: blob prep: refactor getting pages and attaching backing") deb2464e4c6d ("drm/virtio: report uuid in debugfs") c84adb304c10 ("drm/virtio: Support virtgpu exported resources") 0a19b068acc4 ("Merge tag 'drm-misc-next-2020-06-19' of git://anongit.freedesktop.org/drm/drm-misc into drm-next")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 52531258318ed59a2dc5a43df2eaf0eb1d65438e Mon Sep 17 00:00:00 2001 From: Rob Clark robdclark@chromium.org Date: Fri, 16 Dec 2022 15:33:55 -0800 Subject: [PATCH] drm/virtio: Fix GEM handle creation UAF
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...
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c index 5d05093014ac..9f4a90493aea 100644 --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c @@ -358,10 +358,18 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data, drm_gem_object_release(obj); return ret; } - drm_gem_object_put(obj);
rc->res_handle = qobj->hw_res_handle; /* similiar to a VM address */ rc->bo_handle = handle; + + /* + * 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(obj); + return 0; }
@@ -723,11 +731,18 @@ static int virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev, drm_gem_object_release(obj); return ret; } - drm_gem_object_put(obj);
rc_blob->res_handle = bo->hw_res_handle; rc_blob->bo_handle = handle;
+ /* + * 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(obj); + return 0; }