| Message ID | 20190430102145.7423-1-oneukum@suse.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [PATCHv2] UAS: fix alignment of scatter/gather segments | expand |
On Tue, Apr 30, 2019 at 12:21:45PM +0200, Oliver Neukum wrote: > 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: 115bb1ffa54ac ("USB: Add UAS driver") Shouldn't this be: Fixes: 115bb1ffa54c ("USB: Add UAS driver") The sha1 you put here isn't valid :(
On Tue, 30 Apr 2019, Oliver Neukum wrote: > 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 s/unlikelier/less likely/ A matter of English grammatical style -- it might be even better to write: "... as UAS is less likely to run ...". > 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: 115bb1ffa54ac ("USB: Add UAS driver") > Signed-off-by: Oliver Neukum <oneukum@suse.com> > --- > drivers/usb/storage/uas.c | 35 ++++++++++++++++++++++------------- > 1 file changed, 22 insertions(+), 13 deletions(-) > > diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c > index 6d71b8fff9df..3856f34b89b8 100644 > --- a/drivers/usb/storage/uas.c > +++ b/drivers/usb/storage/uas.c > @@ -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. Spaces vs. tabs. Alan Stern > + * 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));
diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c index 6d71b8fff9df..3856f34b89b8 100644 --- a/drivers/usb/storage/uas.c +++ b/drivers/usb/storage/uas.c @@ -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));
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: 115bb1ffa54ac ("USB: Add UAS driver") Signed-off-by: Oliver Neukum <oneukum@suse.com> --- drivers/usb/storage/uas.c | 35 ++++++++++++++++++++++------------- 1 file changed, 22 insertions(+), 13 deletions(-)