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 <oneu...@suse.com>
---
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.
+ */
+
+ 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
