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Subject[PATCH 5.10 069/120] xhci: fix bounce buffer usage for non-sg list case
Date
From: Mathias Nyman <mathias.nyman@linux.intel.com>

commit d4a610635400ccc382792f6be69427078541c678 upstream.

xhci driver may in some special cases need to copy small amounts
of payload data to a bounce buffer in order to meet the boundary
and alignment restrictions set by the xHCI specification.

In the majority of these cases the data is in a sg list, and
driver incorrectly assumed data is always in urb->sg when using
the bounce buffer.

If data instead is contiguous, and in urb->transfer_buffer, we may still
need to bounce buffer a small part if data starts very close (less than
packet size) to a 64k boundary.

Check if sg list is used before copying data to/from it.

Fixes: f9c589e142d0 ("xhci: TD-fragment, align the unsplittable case with a bounce buffer")
Cc: stable@vger.kernel.org
Reported-by: Andreas Hartmann <andihartmann@01019freenet.de>
Tested-by: Andreas Hartmann <andihartmann@01019freenet.de>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20210203113702.436762-2-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/host/xhci-ring.c | 31 ++++++++++++++++++++-----------
1 file changed, 20 insertions(+), 11 deletions(-)

--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -699,11 +699,16 @@ static void xhci_unmap_td_bounce_buffer(
dma_unmap_single(dev, seg->bounce_dma, ring->bounce_buf_len,
DMA_FROM_DEVICE);
/* for in tranfers we need to copy the data from bounce to sg */
- len = sg_pcopy_from_buffer(urb->sg, urb->num_sgs, seg->bounce_buf,
- seg->bounce_len, seg->bounce_offs);
- if (len != seg->bounce_len)
- xhci_warn(xhci, "WARN Wrong bounce buffer read length: %zu != %d\n",
- len, seg->bounce_len);
+ if (urb->num_sgs) {
+ len = sg_pcopy_from_buffer(urb->sg, urb->num_sgs, seg->bounce_buf,
+ seg->bounce_len, seg->bounce_offs);
+ if (len != seg->bounce_len)
+ xhci_warn(xhci, "WARN Wrong bounce buffer read length: %zu != %d\n",
+ len, seg->bounce_len);
+ } else {
+ memcpy(urb->transfer_buffer + seg->bounce_offs, seg->bounce_buf,
+ seg->bounce_len);
+ }
seg->bounce_len = 0;
seg->bounce_offs = 0;
}
@@ -3275,12 +3280,16 @@ static int xhci_align_td(struct xhci_hcd

/* create a max max_pkt sized bounce buffer pointed to by last trb */
if (usb_urb_dir_out(urb)) {
- len = sg_pcopy_to_buffer(urb->sg, urb->num_sgs,
- seg->bounce_buf, new_buff_len, enqd_len);
- if (len != new_buff_len)
- xhci_warn(xhci,
- "WARN Wrong bounce buffer write length: %zu != %d\n",
- len, new_buff_len);
+ if (urb->num_sgs) {
+ len = sg_pcopy_to_buffer(urb->sg, urb->num_sgs,
+ seg->bounce_buf, new_buff_len, enqd_len);
+ if (len != new_buff_len)
+ xhci_warn(xhci, "WARN Wrong bounce buffer write length: %zu != %d\n",
+ len, new_buff_len);
+ } else {
+ memcpy(seg->bounce_buf, urb->transfer_buffer + enqd_len, new_buff_len);
+ }
+
seg->bounce_dma = dma_map_single(dev, seg->bounce_buf,
max_pkt, DMA_TO_DEVICE);
} else {

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