Patch "xhci: fix off by one error in TRB DMA address boundary check" has been added to the 3.14-stable tree

Patch "xhci: fix off by one error in TRB DMA address boundary check" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    xhci: fix off by one error in TRB DMA address boundary check

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     xhci-fix-off-by-one-error-in-trb-dma-address-boundary-check.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 7895086afde2a05fa24a0e410d8e6b75ca7c8fdd Mon Sep 17 00:00:00 2001
From: Mathias Nyman <mathias.nyman@linux.intel.com>
Date: Mon, 3 Aug 2015 16:07:48 +0300
Subject: xhci: fix off by one error in TRB DMA address boundary check
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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

commit 7895086afde2a05fa24a0e410d8e6b75ca7c8fdd upstream.

We need to check that a TRB is part of the current segment
before calculating its DMA address.

Previously a ring segment didn't use a full memory page, and every
new ring segment got a new memory page, so the off by one
error in checking the upper bound was never seen.

Now that we use a full memory page, 256 TRBs (4096 bytes), the off by one
didn't catch the case when a TRB was the first element of the next segment.

This is triggered if the virtual memory pages for a ring segment are
next to each in increasing order where the ring buffer wraps around and
causes errors like:

[  106.398223] xhci_hcd 0000:00:14.0: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 0 comp_code 1
[  106.398230] xhci_hcd 0000:00:14.0: Looking for event-dma fffd3000 trb-start fffd4fd0 trb-end fffd5000 seg-start fffd4000 seg-end fffd4ff0

The trb-end address is one outside the end-seg address.

Tested-by: Arkadiusz Miśkiewicz <arekm@maven.pl>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/host/xhci-ring.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -86,7 +86,7 @@ dma_addr_t xhci_trb_virt_to_dma(struct x
 		return 0;
 	/* offset in TRBs */
 	segment_offset = trb - seg->trbs;
-	if (segment_offset > TRBS_PER_SEGMENT)
+	if (segment_offset >= TRBS_PER_SEGMENT)
 		return 0;
 	return seg->dma + (segment_offset * sizeof(*trb));
 }


Patches currently in stable-queue which might be from mathias.nyman@linux.intel.com are

queue-3.14/xhci-fix-off-by-one-error-in-trb-dma-address-boundary-check.patch