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From: Dexuan Cui <decui@microsoft.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>,
	KY Srinivasan <kys@microsoft.com>,
	"devel@linuxdriverproject.org" <devel@linuxdriverproject.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Jason Wang <jasowang@redhat.com>
Subject: RE: [PATCH 2/4] Drivers: hv: vmbus: do not lose rescind offer on failure in vmbus_process_offer()
Date: Wed, 4 Feb 2015 07:42:36 +0000	[thread overview]
Message-ID: <F792CF86EFE20D4AB8064279AFBA51C61F33A673@HKNPRD3002MB017.064d.mgd.msft.net> (raw)
In-Reply-To: <1422982839-3948-3-git-send-email-vkuznets@redhat.com>

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Wednesday, February 4, 2015 1:01 AM
> To: KY Srinivasan; devel@linuxdriverproject.org
> Cc: Haiyang Zhang; linux-kernel@vger.kernel.org; Dexuan Cui; Jason Wang
> Subject: [PATCH 2/4] Drivers: hv: vmbus: do not lose rescind offer on failure in
> vmbus_process_offer()
> 
> In case we hit a failure condition in vmbus_process_offer() and a rescind offer
> was pending for the channel we just do free_channel() so
> CHANNELMSG_RELID_RELEASED
> will never be send to the host. We have to follow vmbus_process_rescind_offer()
> path anyway.
> 
> To support the change we need to protect list_del in
> vmbus_process_rescind_offer()
> hitting an uninitialized list.
> 
> Reported-by: Dexuan Cui <decui@microsoft.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  drivers/hv/channel_mgmt.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index eb9ce94..fdccd16 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -152,6 +152,7 @@ static struct vmbus_channel *alloc_channel(void)
>  	spin_lock_init(&channel->inbound_lock);
>  	spin_lock_init(&channel->lock);
> 
> +	INIT_LIST_HEAD(&channel->listentry);
>  	INIT_LIST_HEAD(&channel->sc_list);
>  	INIT_LIST_HEAD(&channel->percpu_list);
> 
> @@ -308,6 +309,7 @@ static void vmbus_process_offer(struct work_struct
> *work)
>  	struct vmbus_channel *channel;
>  	bool fnew = true;
>  	bool enq = false;
> +	bool failure = false;
>  	int ret;
>  	unsigned long flags;
> 
> @@ -408,19 +410,33 @@ static void vmbus_process_offer(struct work_struct
> *work)
>  		spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
>  		list_del(&newchannel->listentry);
>  		spin_unlock_irqrestore(&vmbus_connection.channel_lock,
> flags);
> +		/*
> +		 * Init listentry again as vmbus_process_rescind_offer can try
> +		 * doing list_del again.
> +		 */
> +		INIT_LIST_HEAD(&channel->listentry);
>  		kfree(newchannel->device_obj);
> +		newchannel->device_obj = NULL;
>  		goto err_free_chan;
>  	}
> +	goto done_init_rescind;
> +err_free_chan:
> +	failure = true;
>  done_init_rescind:
> +	/*
> +	 * Get additional reference as vmbus_put_channel() can be called
> +	 * either directly or through vmbus_process_rescind_offer().
> +	 */
> +	vmbus_get_channel(newchannel);
>  	spin_lock_irqsave(&newchannel->lock, flags);
here we get the lock.

>  	/* The next possible work is rescind handling */
>  	INIT_WORK(&newchannel->work, vmbus_process_rescind_offer);
>  	/* Check if rescind offer was already received */
>  	if (newchannel->rescind)
>  		queue_work(newchannel->controlwq, &newchannel->work);
> +	else if (failure)
> +		vmbus_put_channel(newchannel);
Here in vmbus_put_channel(), we try to get the same spinlock -- dead lock.

-- Dexuan

>  	spin_unlock_irqrestore(&newchannel->lock, flags);
> -	return;
> -err_free_chan:
>  	vmbus_put_channel(newchannel);
>  }
> 
> --
> 1.9.3


  reply	other threads:[~2015-02-04  7:42 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-03 17:00 [PATCH 0/4] Drivers: hv: Further protection for the rescind path Vitaly Kuznetsov
2015-02-03 17:00 ` [PATCH 1/4] Drivers: hv: vmbus: implement get/put usage workflow for vmbus channels Vitaly Kuznetsov
2015-02-04  8:18   ` Dexuan Cui
2015-02-04  9:32     ` Vitaly Kuznetsov
2015-02-04  9:54       ` Dexuan Cui
2015-02-04  9:14   ` Jason Wang
2015-02-04  9:33     ` Vitaly Kuznetsov
2015-02-03 17:00 ` [PATCH 2/4] Drivers: hv: vmbus: do not lose rescind offer on failure in vmbus_process_offer() Vitaly Kuznetsov
2015-02-04  7:42   ` Dexuan Cui [this message]
2015-02-03 17:00 ` [PATCH 3/4] Drivers: hv: vmbus: protect vmbus_get_outgoing_channel() against channel removal Vitaly Kuznetsov
2015-02-04  7:27   ` Dexuan Cui
2015-02-03 17:00 ` [PATCH 4/4] hyperv: netvsc: improve protection against rescind offer Vitaly Kuznetsov
2015-02-04  7:29   ` Dexuan Cui
2015-02-04 18:26 ` [PATCH 0/4] Drivers: hv: Further protection for the rescind path KY Srinivasan
2015-02-05 10:10   ` Vitaly Kuznetsov
2015-02-05 12:44     ` Dexuan Cui
2015-02-05 22:47       ` KY Srinivasan
2015-02-06 14:53         ` Dexuan Cui
2015-02-07 16:27           ` KY Srinivasan
2015-02-05 15:52     ` KY Srinivasan

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