linux-kernel - Re: [RFC PATCH 00/17] Add validation for used length

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Date:   Mon, 17 May 2021 19:40:06 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xie Yongji <xieyongji@...edance.com>
Cc:     jasowang@...hat.com, stefanha@...hat.com, amit@...nel.org,
        arei.gonglei@...wei.com, airlied@...ux.ie, kraxel@...hat.com,
        dan.j.williams@...el.com, johannes@...solutions.net,
        ohad@...ery.com, bjorn.andersson@...aro.org, david@...hat.com,
        vgoyal@...hat.com, miklos@...redi.hu, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 00/17] Add validation for used length

On Mon, May 17, 2021 at 05:08:19PM +0800, Xie Yongji wrote:
> Current virtio device drivers may trust the used length returned
> in virtqueue_get_buf()/virtqueue_get_buf_ctx(). But the used length
> might come from an untrusted device when VDUSE[1] is enabled. To
> protect this case, this series tries to add validation for the
> used length.
> 
> Since many legacy devices will also set the used length incorrectly,
> we did not add the validation unconditionally. Instead, we will do
> the validation only when the device driver needs the used length.
> A NULL len passed to virtqueue_get_buf()/virtqueue_get_buf_ctx()
> will mean the used length is not needed by the device driver.

Can we be more specific? Which drivers have problems when used len
is incorrect? Maybe there's an easier way like validating the length
in the driver ...

> [1] https://lore.kernel.org/kvm/20210331080519.172-1-xieyongji@bytedance.com/
> 
> Xie Yongji (17):
>   virtio_ring: Avoid reading unneeded used length
>   virtio-blk: Remove unused used length
>   virtio_console: Remove unused used length
>   crypto: virtio - Remove unused used length
>   drm/virtio: Remove unused used length
>   caif_virtio: Remove unused used length
>   virtio_net: Remove unused used length
>   mac80211_hwsim: Remove unused used length
>   virtio_pmem: Remove unused used length
>   rpmsg: virtio: Remove unused used length
>   virtio_scsi: Remove unused used length
>   virtio_balloon: Remove unused used length
>   virtio_input: Remove unused used length
>   virtio_mem: Remove unused used length
>   virtiofs: Remove unused used length
>   vsock: Remove unused used length
>   virtio_ring: Add validation for used length
> 
>  drivers/block/virtio_blk.c                 |  3 +--
>  drivers/char/virtio_console.c              | 12 ++++--------
>  drivers/crypto/virtio/virtio_crypto_algs.c |  6 ++----
>  drivers/gpu/drm/virtio/virtgpu_vq.c        |  3 +--
>  drivers/net/caif/caif_virtio.c             |  3 +--
>  drivers/net/virtio_net.c                   | 10 ++++------
>  drivers/net/wireless/mac80211_hwsim.c      |  3 +--
>  drivers/nvdimm/nd_virtio.c                 |  3 +--
>  drivers/rpmsg/virtio_rpmsg_bus.c           |  3 +--
>  drivers/scsi/virtio_scsi.c                 |  3 +--
>  drivers/virtio/virtio_balloon.c            | 21 ++++++++++-----------
>  drivers/virtio/virtio_input.c              |  6 ++----
>  drivers/virtio/virtio_mem.c                |  3 +--
>  drivers/virtio/virtio_ring.c               | 28 +++++++++++++++++++++++-----
>  fs/fuse/virtio_fs.c                        |  6 ++----
>  net/vmw_vsock/virtio_transport.c           |  3 +--
>  16 files changed, 56 insertions(+), 60 deletions(-)
> 
> -- 
> 2.11.0