linux-kernel - [RFC PATCH 6/6] VFIO: use ACCESS_ONCE() to guard access to dev->driver

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Message-Id: <1352555839-18961-6-git-send-email-jiang.liu@huawei.com>
Date:	Sat, 10 Nov 2012 21:57:19 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Alex Williamson <alex.williamson@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiang Liu <jiang.liu@...wei.com>,
	Joerg Roedel <joerg.roedel@....com>,
	Yinghai Lu <yinghai@...nel.org>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Hanjun Guo <guohanjun@...wei.com>
Subject: [RFC PATCH 6/6] VFIO: use ACCESS_ONCE() to guard access to dev->driver

 From: Jiang Liu <jiang.liu@...wei.com>

Comments from dev_driver_string(),
/* dev->driver can change to NULL underneath us because of unbinding,
 * so be careful about accessing it.
 */

So use ACCESS_ONCE() to guard access to dev->driver field.

Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
---
 drivers/vfio/vfio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 18714b9..f158e42 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -520,8 +520,9 @@ static bool vfio_whitelisted_driver(struct device_driver *drv)
 static int vfio_dev_viable(struct device *dev, void *data)
 {
 	struct vfio_device_driver *driver;
+	struct device_driver *drv = ACCESS_ONCE(dev->driver);
 
-	if (!dev->driver || vfio_whitelisted_driver(dev->driver))
+	if (!drv || vfio_whitelisted_driver(drv))
 		return 0;
 
 	mutex_lock(&vfio.device_drivers_lock);
-- 
1.7.9.5

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