Re: [PATCH v2 4/4] virtio-blk: Use blk_validate_block_size() to validate block size

From: Yongji Xie <xieyongji@bytedance.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	Josef Bacik <josef@toxicpanda.com>,
	Jason Wang <jasowang@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Kevin Wolf <kwolf@redhat.com>,
	linux-block@vger.kernel.org, nbd@other.debian.org,
	virtualization <virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH v2 4/4] virtio-blk: Use blk_validate_block_size() to validate block size
Date: Tue, 26 Oct 2021 22:32:56 +0800	[thread overview]
Message-ID: <CACycT3ustr9ddcXJQ6Y6kbVLtkZkvRdJXoPe5zOkSfi_KzaD2w@mail.gmail.com> (raw)
In-Reply-To: <20211025130321-mutt-send-email-mst@kernel.org>

On Tue, Oct 26, 2021 at 1:08 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Oct 25, 2021 at 10:25:06PM +0800, Xie Yongji wrote:
> > The block layer can't support the block size larger than
>
> the block size -> block sizes, or a block size
>
> > page size yet.
>
> And to add to that, a block size that's too small or
> not a power of two won't work either, right?
> Mention that too.
>

OK.

>
> > If an untrusted device
>
> nothing to do with trust. A misconfigured device.
>

I see.

> > presents an invalid
> > block size in configuration space, it will result in the
> > kernel crash something like below:
> >
> > [  506.154324] BUG: kernel NULL pointer dereference, address: 0000000000000008
> > [  506.160416] RIP: 0010:create_empty_buffers+0x24/0x100
> > [  506.174302] Call Trace:
> > [  506.174651]  create_page_buffers+0x4d/0x60
> > [  506.175207]  block_read_full_page+0x50/0x380
> > [  506.175798]  ? __mod_lruvec_page_state+0x60/0xa0
> > [  506.176412]  ? __add_to_page_cache_locked+0x1b2/0x390
> > [  506.177085]  ? blkdev_direct_IO+0x4a0/0x4a0
> > [  506.177644]  ? scan_shadow_nodes+0x30/0x30
> > [  506.178206]  ? lru_cache_add+0x42/0x60
> > [  506.178716]  do_read_cache_page+0x695/0x740
> > [  506.179278]  ? read_part_sector+0xe0/0xe0
> > [  506.179821]  read_part_sector+0x36/0xe0
> > [  506.180337]  adfspart_check_ICS+0x32/0x320
> > [  506.180890]  ? snprintf+0x45/0x70
> > [  506.181350]  ? read_part_sector+0xe0/0xe0
> > [  506.181906]  bdev_disk_changed+0x229/0x5c0
> > [  506.182483]  blkdev_get_whole+0x6d/0x90
> > [  506.183013]  blkdev_get_by_dev+0x122/0x2d0
> > [  506.183562]  device_add_disk+0x39e/0x3c0
> > [  506.184472]  virtblk_probe+0x3f8/0x79b [virtio_blk]
> > [  506.185461]  virtio_dev_probe+0x15e/0x1d0 [virtio]
> >
> > So this patch tries to use the block layer helper to
> > validate the block size.
>
> I know you are trying to be polite but it's misplaced here.
> Just say what it is:
>
> Use a block layer helper to validate the block size.
>

OK.

> >
> > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > ---
> >  drivers/block/virtio_blk.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index 303caf2d17d0..8b5833997f8e 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> > @@ -815,9 +815,16 @@ static int virtblk_probe(struct virtio_device *vdev)
> >       err = virtio_cread_feature(vdev, VIRTIO_BLK_F_BLK_SIZE,
> >                                  struct virtio_blk_config, blk_size,
> >                                  &blk_size);
> > -     if (!err)
> > +     if (!err) {
> > +             err = blk_validate_block_size(blk_size);
> > +             if (err) {
> > +                     dev_err(&vdev->dev,
> > +                             "get invalid block size: %u\n", blk_size);
>
> Probably hex. Add virtio_blk: and drop "get" here - it's ungrammatical.
>         "virtio_blk: invalid block size: 0x%x\n", blk_size.
>

Will do it.

Thanks,
Yongji