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UAS: fix alignment of scatter/gather segments

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This is the UAS version of

747668dbc0
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: 115bb1ffa5 ("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>
This commit is contained in:
Oliver Neukum 2019-04-30 12:21:45 +02:00 committed by Greg Kroah-Hartman
parent 0f02321e4b
commit 3ae62a4209
1 changed files with 22 additions and 13 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

35
drivers/usb/storage/uas.c
View file

@ -789,24 +789,33 @@ 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));