linux-kernel - [PATCH 3.19.y-ckt 113/160] xen-scsiback: safely copy requests

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Date:	Tue, 19 Jan 2016 17:06:31 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	David Vrabel <david.vrabel@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 113/160] xen-scsiback: safely copy requests

3.19.8-ckt13 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: David Vrabel <david.vrabel@...rix.com>

commit be69746ec12f35b484707da505c6c76ff06f97dc upstream.

The copy of the ring request was lacking a following barrier(),
potentially allowing the compiler to optimize the copy away.

Use RING_COPY_REQUEST() to ensure the request is copied to local
memory.

This is part of XSA155.

Reviewed-by: Juergen Gross <jgross@...e.com>
Signed-off-by: David Vrabel <david.vrabel@...rix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/xen/xen-scsiback.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 8e38499..2d530c1 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -733,7 +733,7 @@ static int scsiback_do_cmd_fn(struct vscsibk_info *info)
 		if (!pending_req)
 			return 1;
 
-		ring_req = *RING_GET_REQUEST(ring, rc);
+		RING_COPY_REQUEST(ring, rc, &ring_req);
 		ring->req_cons = ++rc;
 
 		err = prepare_pending_reqs(info, &ring_req, pending_req);
-- 
1.9.1