From: Oliver Neukum
> Sent: 29 April 2019 13:20
> This is the UAS version of
>
> 747668dbc061b3e62bc1982767a3a1f9815fcf0e
> usb-storage: Set virt_boundary_mask to avoid SG overflows
>
> We are not as likely to be vulnerable as storage, as it is unlikelier
> that UAS is run over a controller without native support for SG,
> but the issue exists.
>
> Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
> ---
> drivers/usb/storage/uas.c | 26 ++++++++++++--------------
> 1 file changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
> index 6d71b8fff9df..ec9c1c7bb156 100644
> --- a/drivers/usb/storage/uas.c
> +++ b/drivers/usb/storage/uas.c
> @@ -789,24 +789,22 @@ static int uas_slave_alloc(struct scsi_device *sdev)
> {
> struct uas_dev_info *devinfo =
> (struct uas_dev_info *)sdev->host->hostdata;
> + int maxp;
>
> sdev->hostdata = devinfo;
>
> /*
> - * USB has unusual DMA-alignment requirements: Although the
> - * starting address of each scatter-gather element doesn't matter,
> - * the length of each element except the last must be divisible
> - * by the Bulk maxpacket value. There's currently no way to
> - * express this by block-layer constraints, so we'll cop out
> - * and simply require addresses to be aligned at 512-byte
> - * boundaries. This is okay since most block I/O involves
> - * hardware sectors that are multiples of 512 bytes in length,
> - * and since host controllers up through USB 2.0 have maxpacket
> - * values no larger than 512.
> - *
> - * But it doesn't suffice for Wireless USB, where Bulk maxpacket
> - * values can be as large as 2048. To make that work properly
> - * will require changes to the block layer.
> + * USB has unusual scatter-gather requirements: the length of each
> + * scatterlist element except the last must be divisible by the
> + * Bulk maxpacket value. Fortunately this value is always a
> + * power of 2. Inform the block layer about this requirement.
> + */
That isn't the correct restriction for XHCI.
It has its own perverse restrictions.
I think they are all handled within the xhci driver.
David
> +
> + maxp = usb_maxpacket(devinfo->udev, devinfo->data_in_pipe, 0);
> + blk_queue_virt_boundary(sdev->request_queue, maxp - 1);
> +
> + /*
> + * This one is for the controllers. We assume 512 is always good.
> */
> blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));
>
> --
> 2.16.4
-
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