From: Oliver Neukum oneukum@suse.com
commit 3ae62a42090f1ed48e2313ed256a1182a85fb575 upstream.
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. The issue has been existing since the inception of the driver.
Fixes: 115bb1ffa54c ("USB: Add UAS driver") Signed-off-by: Oliver Neukum oneukum@suse.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/usb/storage/uas.c | 38 ++++++++++++++++++++++++-------------- 1 file changed, 24 insertions(+), 14 deletions(-)
--- a/drivers/usb/storage/uas.c +++ b/drivers/usb/storage/uas.c @@ -772,23 +772,33 @@ static int uas_slave_alloc(struct scsi_d { 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. + /* + * We have two requirements here. We must satisfy the requirements + * of the physical HC and the demands of the protocol, as we + * definitely want no additional memory allocation in this path + * ruling out using bounce buffers. + * + * For a transmission on USB to continue we must never send + * a package that is smaller than maxpacket. Hence the length of each + * scatterlist element except the last must be divisible by the + * Bulk maxpacket value. + * If the HC does not ensure that through SG, + * the upper layer must do that. We must assume nothing + * about the capabilities off the HC, so we use the most + * pessimistic requirement. + */ + + maxp = usb_maxpacket(devinfo->udev, devinfo->data_in_pipe, 0); + blk_queue_virt_boundary(sdev->request_queue, maxp - 1); + + /* + * The protocol has no requirements on alignment in the strict sense. + * Controllers may or may not have alignment restrictions. + * As this is not exported, we use an extremely conservative guess. */ blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));