This is a note to let you know that I've just added the patch titled drm/virtio: Fix GEM handle creation UAF to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-virtio-fix-gem-handle-creation-uaf.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 52531258318ed59a2dc5a43df2eaf0eb1d65438e Mon Sep 17 00:00:00 2001 From: Rob Clark <robdclark@xxxxxxxxxxxx> Date: Fri, 16 Dec 2022 15:33:55 -0800 Subject: drm/virtio: Fix GEM handle creation UAF From: Rob Clark <robdclark@xxxxxxxxxxxx> commit 52531258318ed59a2dc5a43df2eaf0eb1d65438e upstream. 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@xxxxxxxxxxxx> Reviewed-by: Chia-I Wu <olvaffe@xxxxxxxxx> Fixes: 62fb7a5e1096 ("virtio-gpu: add 3d/virgl support") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20221216233355.542197-2-robdclark@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/virtio/virtgpu_ioctl.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c @@ -292,10 +292,18 @@ static int virtio_gpu_resource_create_io 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; } @@ -656,11 +664,18 @@ static int virtio_gpu_resource_create_bl 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; } Patches currently in stable-queue which might be from robdclark@xxxxxxxxxxxx are queue-5.15/drm-virtio-fix-gem-handle-creation-uaf.patch