On 8/23/2021 7:31 AM, Yongji Xie wrote:
On Mon, Aug 23, 2021 at 7:17 AM Max Gurtovoy <mgurtovoy@xxxxxxxxxx> wrote:
On 8/9/2021 1:16 PM, 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.
This is not clear to me. What is untrusted device ? is it a buggy device ?
A buggy device, the devices in an encrypted VM, or a userspace device
created by VDUSE [1].
[1] https://lore.kernel.org/kvm/20210818120642.165-1-xieyongji@xxxxxxxxxxxxx/
if it's a userspace device, why don't you fix its control path code
instead of adding workarounds in the kernel driver ?
What is the return value for the blk_size in this case that you try to
override ?
The value that is larger than PAGE_SIZE. I think the block layer can
not handle the block size that is larger than PAGE_SIZE correctly,
e.g. in block_read_full_page().
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@xxxxxxxxxxxxx>
---
drivers/block/virtio_blk.c | 39 +++++++++++++++++++++++++++++++++------
1 file changed, 33 insertions(+), 6 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 4b49df2dfd23..afb37aac09e8 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -692,6 +692,28 @@ static const struct blk_mq_ops virtio_mq_ops = {
static unsigned int virtblk_queue_depth;
module_param_named(queue_depth, virtblk_queue_depth, uint, 0444);
+static int virtblk_validate(struct virtio_device *vdev)
+{
+ u32 blk_size;
+
+ if (!vdev->config->get) {
+ dev_err(&vdev->dev, "%s failure: config access disabled\n",
+ __func__);
+ return -EINVAL;
+ }
+
+ if (!virtio_has_feature(vdev, VIRTIO_BLK_F_BLK_SIZE))
+ return 0;
+
+ blk_size = virtio_cread32(vdev,
+ offsetof(struct virtio_blk_config, blk_size));
+
+ if (blk_size < SECTOR_SIZE || blk_size > PAGE_SIZE)
+ __virtio_clear_bit(vdev, VIRTIO_BLK_F_BLK_SIZE);
is it PAGE_SIZE or SZ_4K ?
Do we support a 64K blk size (PPC PAGE_SIZE)
I think PAGE_SIZE should be OK here. I didn't see a hard 4K limitation
in the kernel. NBD did the same check:
static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, loff_t blksize)
{
if (!blksize)
blksize = NBD_DEF_BLKSIZE;
if (blksize < 512 || blksize > PAGE_SIZE || !is_power_of_2(blksize))
return -EINVAL;
Thanks,
Yongji
