Date: Tue, 12 Feb 2013 17:07:41 -0500
To: Steve Dickson <SteveD@redhat.com>
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 06/15] NFSv4: Introduce new label structure
Message-ID: <20130212220741.GJ10267@fieldses.org>
References: <1360327163-20360-1-git-send-email-SteveD@redhat.com>
 <1360327163-20360-7-git-send-email-SteveD@redhat.com>
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In-Reply-To: <1360327163-20360-7-git-send-email-SteveD@redhat.com>
From: "J. Bruce Fields" <bfields@fieldses.org>
Sender: linux-nfs-owner@vger.kernel.org

On Fri, Feb 08, 2013 at 07:39:14AM -0500, Steve Dickson wrote:
> From: David Quigley <dpquigl@davequigley.com>
> 
> In order to mimic the way that NFSv4 ACLs are implemented we have created a
> structure to be used to pass label data up and down the call chain. This patch
> adds the new structure and new members to the required NFSv4 call structures.
> 
> Signed-off-by: Matthew N. Dodd <Matthew.Dodd@sparta.com>
> Signed-off-by: Miguel Rodel Felipe <Rodel_FM@dsi.a-star.edu.sg>
> Signed-off-by: Phua Eu Gene <PHUA_Eu_Gene@dsi.a-star.edu.sg>
> Signed-off-by: Khin Mi Mi Aung <Mi_Mi_AUNG@dsi.a-star.edu.sg>
> ---
>  fs/nfs/inode.c            | 33 +++++++++++++++++++++++++++++++++
>  include/linux/nfs4.h      |  7 +++++++
>  include/linux/nfs_fs.h    | 17 +++++++++++++++++
>  include/linux/nfs_xdr.h   | 21 +++++++++++++++++++++
>  include/uapi/linux/nfs4.h |  2 +-
>  5 files changed, 79 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> index ebeb94c..8d5f01b 100644
> --- a/fs/nfs/inode.c
> +++ b/fs/nfs/inode.c
> @@ -255,6 +255,39 @@ nfs_init_locked(struct inode *inode, void *opaque)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_NFS_V4_SECURITY_LABEL
> +struct nfs4_label *nfs4_label_alloc(struct nfs_server *server, gfp_t flags)
> +{
> +	struct nfs4_label *label = NULL;
> +
> +	if (!(server->caps & NFS_CAP_SECURITY_LABEL))
> +		return label;
> +
> +	label = kzalloc(NFS4_MAXLABELLEN, flags);
> +	if (label == NULL)
> +		return ERR_PTR(-ENOMEM);
> +
> +	label->label = (char *)(label + 1);
> +	label->len = NFS4_MAXLABELLEN;

If you're expecting to be able to store up to NFS4_MAXLABELLEN of data
after the end of the struct, then you want:

	label = kzalloc(sizeof(struct nfs4_label) + NFS4_MAXLABELLEN, flags);

> +
> +	return label;
> +}
> +EXPORT_SYMBOL_GPL(nfs4_label_alloc);
> +
> +void nfs4_label_init(struct nfs4_label *label)
> +{
> +	if (label && label->label) {
> +		/* 0 is the null format meaning that the data is not
> +		to be translated */
> +		label->lfs = 0;
> +		label->pi = 0;
> +		label->len = NFS4_MAXLABELLEN;

This logic seems a little odd to me; why would we pass NULL to this?
Why would we skip the other initialization in the !label->label case?
Why is NFS4_MAXLABELLEN the default?  (And wasn't that just set in
nfs4_label_alloc?)

But OK maybe I need to read the rest of the patches.

> +	}
> +	return;
> +}
> +EXPORT_SYMBOL_GPL(nfs4_label_init);
> +#endif

> diff --git a/include/uapi/linux/nfs4.h b/include/uapi/linux/nfs4.h
> index 788128e..b8014a2 100644
> --- a/include/uapi/linux/nfs4.h
> +++ b/include/uapi/linux/nfs4.h
> @@ -25,7 +25,7 @@
>  #define NFS4_MAXNAMLEN		NAME_MAX
>  #define NFS4_OPAQUE_LIMIT	1024
>  #define NFS4_MAX_SESSIONID_LEN	16
> -
> +#define NFS4_MAXLABELLEN (4095 - offsetof(struct nfs4_label , label))

The way you've defined things, that should be just

			    (4095 - sizeof(struct nfs4_label))

(Is there typically some more alloc overhead that would push this
allocation over 4k?  I don't know well enough how the allocator(s) work
to answer that.)

--b.

>  #define NFS4_ACCESS_READ        0x0001
>  #define NFS4_ACCESS_LOOKUP      0x0002
>  #define NFS4_ACCESS_MODIFY      0x0004