This is a note to let you know that I've just added the patch titled
Drivers: hv: vmbus: Fix a race condition when unregistering a device
to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-next branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will also be merged in the next major kernel release
during the merge window.
If you have any questions about this process, please let me know.
>From 04a258c162a85c0f4ae56be67634dc43c9a4fa9b Mon Sep 17 00:00:00 2001
From: Vitaly Kuznetsov <[email protected]>
Date: Tue, 4 Nov 2014 13:40:11 +0100
Subject: 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 <[email protected]>
Signed-off-by: K. Y. Srinivasan <[email protected]>
Cc: <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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 a2d1a9612c86..d36ce6835fb7 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;
--
2.1.3
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