linux-kernel - [PATCH 3.4 035/176] driver core: Fix unbalanced device reference in drivers

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Message-Id: <1428569224-23820-35-git-send-email-lizf@kernel.org>
Date:	Thu,  9 Apr 2015 16:44:43 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Alex Williamson <alex.williamson@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 035/176] driver core: Fix unbalanced device reference in drivers_probe

From: Alex Williamson <alex.williamson@...hat.com>

3.4.107-rc1 review patch.  If anyone has any objections, please let me know.

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


commit bb34cb6bbd287b57e955bc5cfd42fcde6aaca279 upstream.

bus_find_device_by_name() acquires a device reference which is never
released.  This results in an object leak, which on older kernels
results in failure to release all resources of PCI devices.  libvirt
uses drivers_probe to re-attach devices to the host after assignment
and is therefore a common trigger for this leak.

Example:

# cd /sys/bus/pci/
# dmesg -C
# echo 1 > devices/0000\:01\:00.0/sriov_numvfs
# echo 0 > devices/0000\:01\:00.0/sriov_numvfs
# dmesg | grep 01:10
 pci 0000:01:10.0: [8086:10ca] type 00 class 0x020000
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_add_internal: parent: '0000:00:01.0', set: 'devices'
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_cleanup, parent           (null)
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): calling ktype release
 kobject: '0000:01:10.0': free name

[kobject freed as expected]

# dmesg -C
# echo 1 > devices/0000\:01\:00.0/sriov_numvfs
# echo 0000:01:10.0 > drivers_probe
# echo 0 > devices/0000\:01\:00.0/sriov_numvfs
# dmesg | grep 01:10
 pci 0000:01:10.0: [8086:10ca] type 00 class 0x020000
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_add_internal: parent: '0000:00:01.0', set: 'devices'
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'

[no free]

Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 drivers/base/bus.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index b850cec..0f682f7 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -245,13 +245,15 @@ static ssize_t store_drivers_probe(struct bus_type *bus,
 				   const char *buf, size_t count)
 {
 	struct device *dev;
+	int err = -EINVAL;
 
 	dev = bus_find_device_by_name(bus, NULL, buf);
 	if (!dev)
 		return -ENODEV;
-	if (bus_rescan_devices_helper(dev, NULL) != 0)
-		return -EINVAL;
-	return count;
+	if (bus_rescan_devices_helper(dev, NULL) == 0)
+		err = count;
+	put_device(dev);
+	return err;
 }
 #endif
 
-- 
1.9.1

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