Message-ID: <51203168.7050204@RedHat.com>
Date: Sat, 16 Feb 2013 20:24:56 -0500
From: Steve Dickson <SteveD@redhat.com>
MIME-Version: 1.0
To: "J. Bruce Fields" <bfields@fieldses.org>
CC: Trond Myklebust <Trond.Myklebust@netapp.com>,
        "J. Bruce Fields" <bfields@redhat.com>,
        "David P. Quigley" <dpquigl@tycho.nsa.gov>,
        Linux NFS list <linux-nfs@vger.kernel.org>,
        Linux FS devel list <linux-fsdevel@vger.kernel.org>,
        Linux Security List <linux-security-module@vger.kernel.org>,
        SELinux List <selinux@tycho.nsa.gov>
Subject: Re: [PATCH 10/15] NFS: Client implementation of Labeled-NFS
References: <1360327163-20360-1-git-send-email-SteveD@redhat.com> <1360327163-20360-11-git-send-email-SteveD@redhat.com> <20130212230346.GN10267@fieldses.org> <511FED8E.7020308@RedHat.com> <20130216223035.GB28824@fieldses.org>
In-Reply-To: <20130216223035.GB28824@fieldses.org>
Content-Type: text/plain; charset=ISO-8859-1
Sender: linux-nfs-owner@vger.kernel.org


On 16/02/13 17:30, J. Bruce Fields wrote:
> On Sat, Feb 16, 2013 at 03:35:26PM -0500, Steve Dickson wrote:
>> On 12/02/13 18:03, J. Bruce Fields wrote:
>>>> +static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
>>>>> +					struct nfs4_label *label)
>>>>> +{
>>>>> +	uint32_t pi = 0;
>>>>> +	uint32_t lfs = 0;
>>>>> +	__u32 len;
>>>>> +	__be32 *p;
>>>>> +	int status = 0;
>>>>> +
>>>>> +	if (unlikely(bitmap[2] & (FATTR4_WORD2_SECURITY_LABEL - 1U)))
>>>>> +		return -EIO;
>>>>> +	if (likely(bitmap[2] & FATTR4_WORD2_SECURITY_LABEL)) {
>>>>> +		p = xdr_inline_decode(xdr, 4);
>>>>> +		if (unlikely(!p))
>>>>> +			goto out_overflow;
>>>>> +		lfs = be32_to_cpup(p++);
>>>>> +		p = xdr_inline_decode(xdr, 4);
>>>>> +		if (unlikely(!p))
>>>>> +			goto out_overflow;
>>>>> +		pi = be32_to_cpup(p++);
>>>>> +		p = xdr_inline_decode(xdr, 4);
>>>>> +		if (unlikely(!p))
>>>>> +			goto out_overflow;
>>>>> +		len = be32_to_cpup(p++);
>>>>> +		p = xdr_inline_decode(xdr, len);
>>>>> +		if (unlikely(!p))
>>>>> +			goto out_overflow;
>>>>> +		if (len < XDR_MAX_NETOBJ) {
>>>>> +			if (label) {
>>>>> +				nfs4_label_init(label);
>>>>> +				if (label->len < len) {
>>> If I remember the earlier patch right, nfs4_label_init() just set
>>> label->len to NFS4_MAXLABELLEN.
>> Good good catch... XDR_MAX_NETOBJ should be NFS4_MAXLABELLEN.
>>
>>>
>>> Doesn't that overwrite the length that was passed into
>>> nfs4_get_security_label?
>> Yes... the len will be set to the actual size of the label which
>> will be less than NFS4_MAXLABELLEN. So I'm thinking this overwrite 
>> of the is fine.
>>
>> This is the reason nfs4_label_init() resets len to NFS4_MAXLABELLEN
> 
> OK, but then
> 					if (label->len < len)
> is equivalent to
> 					if (NFS4_MAXLABELLEN < len)
> Why are we checking len twice?
I see your point... 

> 
> You may want to just remove nfs4_label_init() entirely.  This is the
> only caller, and it doesn't seem very useful.
Its a useful way to reset len back to NFS4_MAXLABELLEN as well as 
lfs and pi back to zero... 

steved.