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

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On Mon, Oct 25, 2021 at 9:20 PM Michael S. Tsirkin <mst@xxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > ---
> >  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



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