linux-kernel - [PATCH 4.9 42/92] xhci: Fix false warning message about wrong bounce buffer write length

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Message-Id: <20191016214832.941082581@linuxfoundation.org>
Date:   Wed, 16 Oct 2019 14:50:15 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Mathias Nyman <mathias.nyman@...ux.intel.com>
Subject: [PATCH 4.9 42/92] xhci: Fix false warning message about wrong bounce buffer write length

From: Mathias Nyman <mathias.nyman@...ux.intel.com>

commit c03101ff4f74bb30679c1a03d551ecbef1024bf6 upstream.

The check printing out the "WARN Wrong bounce buffer write length:"
uses incorrect values when comparing bytes written from scatterlist
to bounce buffer. Actual copied lengths are fine.

The used seg->bounce_len will be set to equal new_buf_len a few lines later
in the code, but is incorrect when doing the comparison.

The patch which added this false warning was backported to 4.8+ kernels
so this should be backported as far as well.

Cc: <stable@...r.kernel.org> # v4.8+
Fixes: 597c56e372da ("xhci: update bounce buffer with correct sg num")
Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
Link: https://lore.kernel.org/r/1570190373-30684-2-git-send-email-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/host/xhci-ring.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3200,10 +3200,10 @@ static int xhci_align_td(struct xhci_hcd
 	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 != seg->bounce_len)
+		if (len != new_buff_len)
 			xhci_warn(xhci,
 				"WARN Wrong bounce buffer write length: %zu != %d\n",
-				len, seg->bounce_len);
+				len, new_buff_len);
 		seg->bounce_dma = dma_map_single(dev, seg->bounce_buf,
 						 max_pkt, DMA_TO_DEVICE);
 	} else {