> -----Original Message----- > From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] > Sent: Tuesday, November 4, 2014 4:40 AM > To: KY Srinivasan; Haiyang Zhang > Cc: Greg Kroah-Hartman; devel@xxxxxxxxxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx > 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(). > Thank you. > Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> > --- > 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 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
