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

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Yongji Xie <xieyongji@bytedance.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 4/4] virtio-blk: Use blk_validate_block_size() to validate block size
Date: Mon, 25 Oct 2021 13:21:09 -0400	[thread overview]
Message-ID: <20211025131446-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CACycT3smA7sSdp-8BKUtN4OW7nkUX+NaW_x9JzfvVgUvM9Yh7A@mail.gmail.com>

On Mon, Oct 25, 2021 at 09:47:34PM +0800, Yongji Xie wrote:
> On Mon, Oct 25, 2021 at 9:20 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Mon, Oct 25, 2021 at 05:43:06PM +0800, Xie Yongji wrote:
> > > The block layer can't support the block size larger than
> > > page size yet. If an untrusted device 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.
> > >
> > > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > > ---
> > >  drivers/block/virtio_blk.c | 7 +++++--
> > >  1 file changed, 5 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > > index 303caf2d17d0..5bcacefe969e 100644
> > > --- a/drivers/block/virtio_blk.c
> > > +++ b/drivers/block/virtio_blk.c
> > > @@ -815,9 +815,12 @@ 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) {
> > > +             if (blk_validate_block_size(blk_size))
> > > +                     goto out_cleanup_disk;
> > > +
> >
> >
> > Did you test this with an invalid blk size? It seems unlikely that it
> > fails properly the way you'd expect.
> >
> 
> Oops... Sorry, I just checked whether the block device is created with
> invalid block size.
> 
> Will send v2 soon!
> 
> Thanks,
> Yongji

Please avoid doing that in the future. Posting untested patches is only
acceptable if you make it abundantly clear that they are untested.

-- 
MST