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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 3/4] Drivers: hv: vmbus: protect vmbus_get_outgoing_channel() against channel removal
Date: Wed, 4 Feb 2015 07:27:30 +0000	[thread overview]
Message-ID: <F792CF86EFE20D4AB8064279AFBA51C61F33A622@HKNPRD3002MB017.064d.mgd.msft.net> (raw)
In-Reply-To: <1422982839-3948-4-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 3/4] Drivers: hv: vmbus: protect vmbus_get_outgoing_channel()
> against channel removal
> 
> list_for_each_safe() we have in vmbus_get_outgoing_channel() works, however,
> we
> are not protected against the channel being removed (e.g. after receiving
> rescind
> offer). Users of this function (storvsc_do_io() is the only one at this moment)
> can get a link to an already freed channel. Make vmbus_get_outgoing_channel()
> search holding primary->lock as child channels are not being freed unless they're
> removed from parent's list.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  drivers/hv/channel_mgmt.c  | 10 +++++++---
>  drivers/scsi/storvsc_drv.c |  2 ++
>  2 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index fdccd16..af6243c 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -881,18 +881,20 @@ cleanup:
>   */
>  struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel
> *primary)
>  {
> -	struct list_head *cur, *tmp;
> +	struct list_head *cur;
>  	int cur_cpu;
>  	struct vmbus_channel *cur_channel;
>  	struct vmbus_channel *outgoing_channel = primary;
>  	int cpu_distance, new_cpu_distance;
> +	unsigned long flags;
> 
>  	if (list_empty(&primary->sc_list))
> -		return outgoing_channel;
> +		return vmbus_get_channel(outgoing_channel);
> 
>  	cur_cpu = hv_context.vp_index[get_cpu()];
>  	put_cpu();
> -	list_for_each_safe(cur, tmp, &primary->sc_list) {
> +	spin_lock_irqsave(&primary->lock, flags);
hmm, we should avoid the locking here because it's a performance killer...
How about adding vmbus_get/put_channel() in vmbus_open/close()?

Thanks,
-- Dexuan

> +	list_for_each(cur, &primary->sc_list) {
>  		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
>  		if (cur_channel->state != CHANNEL_OPENED_STATE)
>  			continue;
> @@ -913,6 +915,8 @@ struct vmbus_channel
> *vmbus_get_outgoing_channel(struct vmbus_channel *primary)
> 
>  		outgoing_channel = cur_channel;
>  	}
> +	outgoing_channel = vmbus_get_channel(outgoing_channel);
> +	spin_unlock_irqrestore(&primary->lock, flags);
> 
>  	return outgoing_channel;
>  }
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 4cff0dd..3b9b851 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1370,6 +1370,8 @@ static int storvsc_do_io(struct hv_device *device,
> 
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
>  	}
> 
> +	vmbus_put_channel(outgoing_channel);
> +
>  	if (ret != 0)
>  		return ret;
> 
> --
> 1.9.3


  reply	other threads:[~2015-02-04  7:43 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
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 [this message]
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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