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Commit c3b3955f authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
Browse files

UAS: fix alignment of scatter/gather segments 



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: 115bb1ff ("USB: Add UAS driver")
Signed-off-by: default avatarOliver Neukum <oneukum@suse.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 38f092c4

drivers/usb/storage/uas.c

+22 −13
Original line number Diff line number Diff line
@@ -796,24 +796,33 @@ 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.

	 * 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.

	 *

	 * 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.

	 * 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));