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
