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From:   Yongji Xie <xieyongji@bytedance.com>
Date:   Tue, 5 Oct 2021 23:45:31 +0800
Message-ID: <CACycT3tUSem1ovOjykmg2Y5+uUaqsiDkFAjrt7SFkJCc9LGbAA@mail.gmail.com>
Subject: Re: [PATCH v5] virtio-blk: Add validation for block size in config space
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Jason Wang <jasowang@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        virtualization <virtualization@lists.linux-foundation.org>,
        linux-block@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Kevin Wolf <kwolf@redhat.com>, Christoph Hellwig <hch@lst.de>,
        Jens Axboe <axboe@kernel.dk>
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On Tue, Oct 5, 2021 at 6:42 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Oct 04, 2021 at 11:27:29AM -0400, Michael S. Tsirkin wrote:
> > On Mon, Aug 09, 2021 at 06:16:09PM +0800, Xie Yongji wrote:
> > > An untrusted device might presents an invalid block size
> > > in configuration space. This tries to add validation for it
> > > in the validate callback and clear the VIRTIO_BLK_F_BLK_SIZE
> > > feature bit if the value is out of the supported range.
> > >
> > > And we also double check the value in virtblk_probe() in
> > > case that it's changed after the validation.
> > >
> > > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> >
> > So I had to revert this due basically bugs in QEMU.
> >
> > My suggestion at this point is to try and update
> > blk_queue_logical_block_size to BUG_ON when the size
> > is out of a reasonable range.
> >
> > This has the advantage of fixing more hardware, not just virtio.
> >
>
> Stefan also pointed out this duplicates the logic from
>
>         if (blksize < 512 || blksize > PAGE_SIZE || !is_power_of_2(blksize))
>                 return -EINVAL;
>
>
> and a bunch of other places.
>
>
> Would it be acceptable for blk layer to validate the input
> instead of having each driver do it's own thing?
> Maybe inside blk_queue_logical_block_size?
>

Now the nbd and loop driver will validate the blksize and return error
if it's invalid. But the nvme and null_blk driver just corrects the
blksize to a reasonable range without returning any error. I'm not
sure which way the block layer should follow. Or just simplify the
logic in nbd and loop driver?

Thanks,
Yongji