Re: [PATCH] nfsd4: handle failure to find backchannel

[Kinglong Mee <kinglongmee@gmail.com>]

On 7/17/2014 06:05, J. Bruce Fields wrote:
> On Sat, Jul 12, 2014 at 10:02:17PM +0800, Kinglong Mee wrote:
>> On 7/12/2014 05:16, J. Bruce Fields wrote:
>>> The local variable "ses" will be left NULL here in the case we fail to
>>> find a connection.  Spotted by a coverity scan.
>>>     
>>> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
>>>
>>> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
>>> index 2c73cae9899d..fe22cd5c42d3 100644
>>> --- a/fs/nfsd/nfs4callback.c
>>> +++ b/fs/nfsd/nfs4callback.c
>>> @@ -1001,14 +1001,18 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
>>>  	}
>>>  	spin_unlock(&clp->cl_lock);
>>>  
>>> +	if (!c)
>>> +		goto out_no_connection;
>>
>> Setting err to -EINVAL maybe better.
>> Otherwise, nfsd4_mark_cb_down will be called with err == 0.
>>
>>>  	err = setup_callback_client(clp, &conn, ses);
>>
>> setup_callback_client also return -EINVAL when ses == NULL with conn.cb_xprt == NULL.
> 
> Thanks, yes, after looking over this carefully I don't believe we can
> call setup_callback_client with ses NULL but conn->cb_xprt non-NULL, so
> this is just a false positive from coverity.

ses and conn->cb_xprt will be set in the same condition before
calling setup_callback_client,

 996         c = __nfsd4_find_backchannel(clp);
 997         if (c) {
 998                 svc_xprt_get(c->cn_xprt);
 999                 conn.cb_xprt = c->cn_xprt;
1000                 ses = c->cn_session;
1001         }
1002         spin_unlock(&clp->cl_lock);
1003
1004         err = setup_callback_client(clp, &conn, ses);

ses and conn->cb_xprt will be NULL or non-NULL in the same time,
so that, call setup_calback_client with ses NULL but conn->cb_xprt non-NULL will not appear.

thanks,
Kinglong Mee

>>> -	if (err) {
>>> -		nfsd4_mark_cb_down(clp, err);
>>> -		return;
>>> -	}
>>> +	if (err)
>>> +		goto out_no_connection;
>>>  	/* Yay, the callback channel's back! Restart any callbacks: */
>>>  	list_for_each_entry(cb, &clp->cl_callbacks, cb_per_client)
>>>  		run_nfsd4_cb(cb);
>>> +	return;
>>> +out_no_connection:
>>> +	nfsd4_mark_cb_down(clp, err);
>>> +	return;
>>>  }
>>>  
>>>  static void nfsd4_do_callback_rpc(struct work_struct *w)
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>