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authorVitaly Kuznetsov <vkuznets@redhat.com>2014-11-04 13:40:11 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-01-16 06:59:32 -0800
commit8a8c38c8e681f36170d6d565c8c50539f7845667 (patch)
treeeb0f7cad75100a296063e9c6b3fbef09d2294004
parent7810e6d8f1390a96e634e66072064c69a6f7d08d (diff)
downloadlinux-linaro-stable-8a8c38c8e681f36170d6d565c8c50539f7845667.tar.gz
Drivers: hv: vmbus: Fix a race condition when unregistering a device
commit 04a258c162a85c0f4ae56be67634dc43c9a4fa9b upstream. 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@redhat.com> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/hv/channel_mgmt.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index fa920469bf10..505fe29c75b0 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -202,9 +202,16 @@ 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;