linux-kernel - [PATCH 3.16.y-ckt 228/254] sunvdc: limit each sg segment to a page

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Message-Id: <1416912004-5928-229-git-send-email-luis.henriques@canonical.com>
Date:	Tue, 25 Nov 2014 10:39:38 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Dwight Engen <dwight.engen@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 228/254] sunvdc: limit each sg segment to a page

3.16.7-ckt2 -stable review patch.  If anyone has any objections, please let me know.

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

From: Dwight Engen <dwight.engen@...cle.com>

commit 5eed69ffd248c9f68f56c710caf07db134aef28b upstream.

ldc_map_sg() could fail its check that the number of pages referred to
by the sg scatterlist was <= the number of cookies.

This fixes the issue by doing a similar thing to the xen-blkfront driver,
ensuring that the scatterlist will only ever contain a segment count <=
port->ring_cookies, and each segment will be page aligned, and <= page
size. This ensures that the scatterlist is always mappable.

Orabug: 19347817
OraBZ: 15945

Signed-off-by: Dwight Engen <dwight.engen@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/block/sunvdc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/sunvdc.c b/drivers/block/sunvdc.c
index 1616ad091a5e..1a9360da1f54 100644
--- a/drivers/block/sunvdc.c
+++ b/drivers/block/sunvdc.c
@@ -747,6 +747,10 @@ static int probe_disk(struct vdc_port *port)
 
 	port->disk = g;
 
+	/* Each segment in a request is up to an aligned page in size. */
+	blk_queue_segment_boundary(q, PAGE_SIZE - 1);
+	blk_queue_max_segment_size(q, PAGE_SIZE);
+
 	blk_queue_max_segments(q, port->ring_cookies);
 	blk_queue_max_hw_sectors(q, port->max_xfer_size);
 	g->major = vdc_major;
-- 
2.1.0

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