[PATCH 2.6.32 09/38] [PATCH 09/38] xhci: fix off by one error in TRB DMA address boundary check

From: Willy Tarreau <w@1wt.eu>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: "Arkadiusz MiÅ›kiewicz" <arekm@maven.pl>,
	"Mathias Nyman" <mathias.nyman@linux.intel.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Ben Hutchings" <ben@decadent.org.uk>, "Willy Tarreau" <w@1wt.eu>
Subject: [PATCH 2.6.32 09/38] [PATCH 09/38] xhci: fix off by one error in TRB DMA address boundary check
Date: Mon, 30 Nov 2015 01:25:06 +0000	[thread overview]
Message-ID: <20151129214703.269304855@1wt.eu> (raw)
In-Reply-To: <8acf8256ccc72771a80b7851061027bc@local>

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

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 MiÅ›kiewicz <arekm@maven.pl>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
(cherry picked from commit 6e3ae6256145b5597bee0296eb5fc384cd86aa3d)
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
 drivers/usb/host/xhci-ring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 38fb682..fa22638 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -80,7 +80,7 @@ dma_addr_t xhci_trb_virt_to_dma(struct xhci_segment *seg,
 		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));
 }
-- 
1.7.12.2.21.g234cd45.dirty



