linux-kernel - Re: [PATCH 2/3] SUNRPC: check rpcbind clients usage counter before decrement

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Date:	Tue, 1 May 2012 12:20:29 +0400
From:	Stanislav Kinsbursky <skinsbursky@...allels.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
CC:	"Trond.Myklebust@...app.com" <Trond.Myklebust@...app.com>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...nvz.org" <devel@...nvz.org>
Subject: Re: [PATCH 2/3] SUNRPC: check rpcbind clients usage counter before
 decrement

01.05.2012 01:45, J. Bruce Fields написал:
> On Fri, Apr 27, 2012 at 06:08:13PM +0400, Stanislav Kinsbursky wrote:
>> On 27.04.2012 17:55, J. Bruce Fields wrote:
>>> On Wed, Apr 25, 2012 at 05:37:49PM +0400, Stanislav Kinsbursky wrote:
>>>> Registering service with svc_bind() can fail. In this case service will be
>>>> destroyed and during destruction it will try to unregister itself from rpcbind.
>>>> In this case unregister have to be skipped.
>>> Isn't this a preexisting bug, in which case perhaps Trond should at it
>>> to his list of bugs to submit now?
>>>
>> Not it's not.
>>
>> Previously, in case of bind operations failure, rpcb_put_local()
>> wasn't called, but service data was destroyed instead:
>>
>> -	if (svc_uses_rpcbind(serv)) {
>> -		if (svc_rpcb_setup(serv, current->nsproxy->net_ns)<  0) {
>> -			kfree(serv->sv_pools);
>> -			kfree(serv);
>> -			return NULL;
>> -		}
>> -		if (!serv->sv_shutdown)
>> -			serv->sv_shutdown = svc_rpcb_cleanup;
>> -	}
>>
>> Now (with svc_bind() introduction) service can be created, but
>> svc_bind() could fail. And thus svc_destroy() have to be called.
>> Which will call rpcb_put_local().
>>
>> And the problem here that svc_bind() can fail before incrementing of
>> rpcb usage counter.
> OK, but then you're fixing a bug that you just introduced with the
> previous patch.
>
> So this should be combined with the previous patch.
>
> --b.

You, probably, right. I'll do this.
Thanks.

>>>> Signed-off-by: Stanislav Kinsbursky<skinsbursky@...allels.com>
>>>>
>>>> ---
>>>>   net/sunrpc/rpcb_clnt.c |   12 +++++++-----
>>>>   1 files changed, 7 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
>>>> index 78ac39f..4c38b33 100644
>>>> --- a/net/sunrpc/rpcb_clnt.c
>>>> +++ b/net/sunrpc/rpcb_clnt.c
>>>> @@ -180,14 +180,16 @@ void rpcb_put_local(struct net *net)
>>>>   	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
>>>>   	struct rpc_clnt *clnt = sn->rpcb_local_clnt;
>>>>   	struct rpc_clnt *clnt4 = sn->rpcb_local_clnt4;
>>>> -	int shutdown;
>>>> +	int shutdown = 0;
>>>>
>>>>   	spin_lock(&sn->rpcb_clnt_lock);
>>>> -	if (--sn->rpcb_users == 0) {
>>>> -		sn->rpcb_local_clnt = NULL;
>>>> -		sn->rpcb_local_clnt4 = NULL;
>>>> +	if (sn->rpcb_users) {
>>>> +		if (--sn->rpcb_users == 0) {
>>>> +			sn->rpcb_local_clnt = NULL;
>>>> +			sn->rpcb_local_clnt4 = NULL;
>>>> +		}
>>>> +		shutdown = !sn->rpcb_users;
>>>>   	}
>>>> -	shutdown = !sn->rpcb_users;
>>>>   	spin_unlock(&sn->rpcb_clnt_lock);
>>>>
>>>>   	if (shutdown) {
>>>>
>>
>> -- 
>> Best regards,
>> Stanislav Kinsbursky

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