linux-kernel - [PATCH] Drivers: hv: vmbus: Fix a race condition when unregistering a device

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1415104811-28142-1-git-send-email-vkuznets@redhat.com>
Date:	Tue,  4 Nov 2014 13:40:11 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devel@...uxdriverproject.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Drivers: hv: vmbus: Fix a race condition when unregistering a device

When build with Debug the following crash is sometimes observed:
Call Trace:
 [<ffffffff812b9600>] string+0x40/0x100
 [<ffffffff812bb038>] vsnprintf+0x218/0x5e0
 [<ffffffff810baf7d>] ? trace_hardirqs_off+0xd/0x10
 [<ffffffff812bb4c1>] vscnprintf+0x11/0x30
 [<ffffffff8107a2f0>] vprintk+0xd0/0x5c0
 [<ffffffffa0051ea0>] ? vmbus_process_rescind_offer+0x0/0x110 [hv_vmbus]
 [<ffffffff8155c71c>] printk+0x41/0x45
 [<ffffffffa004ebac>] vmbus_device_unregister+0x2c/0x40 [hv_vmbus]
 [<ffffffffa0051ecb>] vmbus_process_rescind_offer+0x2b/0x110 [hv_vmbus]
...

This happens due to the following race: between 'if (channel->device_obj)' check
in vmbus_process_rescind_offer() and pr_debug() in vmbus_device_unregister() the
device can disappear. Fix the issue by taking an additional reference to the
device before proceeding to vmbus_device_unregister().

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 drivers/hv/channel_mgmt.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index a2d1a96..d36ce68 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -216,9 +216,16 @@ static void vmbus_process_rescind_offer(struct work_struct *work)
 	unsigned long flags;
 	struct vmbus_channel *primary_channel;
 	struct vmbus_channel_relid_released msg;
+	struct device *dev;
+
+	if (channel->device_obj) {
+		dev = get_device(&channel->device_obj->device);
+		if (dev) {
+			vmbus_device_unregister(channel->device_obj);
+			put_device(dev);
+		}
+	}

-	if (channel->device_obj)
-		vmbus_device_unregister(channel->device_obj);
 	memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
 	msg.child_relid = channel->offermsg.child_relid;
 	msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
-- 
1.9.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/