linux-kernel - Re: [PATCH 08/11] NFS: Introduce lifecycle management for label attribute.

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Date:	Thu, 28 Feb 2008 15:07:47 -0500
From:	Dave Quigley <dpquigl@...ho.nsa.gov>
To:	James Morris <jmorris@...ei.org>
Cc:	hch@...radead.org, viro@....linux.org.uk,
	trond.myklebust@....uio.no, bfields@...ldses.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 08/11] NFS: Introduce lifecycle management for label
	attribute.


On Thu, 2008-02-28 at 12:04 +1100, James Morris wrote:
> On Wed, 27 Feb 2008, David P. Quigley wrote:
> 
> > +#ifdef CONFIG_SECURITY
> > +static inline void nfs_fattr_alloc(struct nfs_fattr *fattr, gfp_t flags)
> > +{
> > +	fattr->label = kzalloc(NFS4_MAXLABELLEN, flags);
> > +	if (fattr->label == NULL)
> > +		panic("Can't allocate security label.");
> > +	fattr->label_len = NFS4_MAXLABELLEN;
> > +}
> 
> A panic here seems like overkill, and also possibly a DoS vector.  I 
> suggest having the calling code handle the allocation failure gracefully.
> 
> > +
> > +#define	nfs_fattr_fini(fattr)	_nfs_fattr_fini(fattr, __FILE__, __LINE__, __func__)
> > +static inline void _nfs_fattr_fini(struct nfs_fattr *fattr,
> > +		const char *file, int line, const char *func)
> > +{
> > +	if ((fattr)->label == NULL) {
> > +		if (fattr->label_len != 0) {
> > +			printk(KERN_WARNING
> > +					"%s:%d %s() nfs_fattr label available (%d)\n",
> > +					file, line, func,
> > +					fattr->label_len);
> > +		}
> > +	} else {
> > +		if (fattr->label_len == NFS4_MAXLABELLEN)
> > +			printk(KERN_WARNING
> > +					"%s:%d %s() nfs_fattr label unused\n",
> > +					file, line, func);
> > +		else if (fattr->label_len != (strlen(fattr->label) + 1))
> > +			printk(KERN_WARNING
> > +				"%s:%d %s() nfs_fattr label size mismatch (label_len %d, strlen %d)\n",
> > +				file, line, func,
> > +				fattr->label_len, strlen(fattr->label) + 1);
> > +
> > +		kfree(fattr->label);
> > +		fattr->label = NULL;
> > +		fattr->label_len = 0;
> > +	}
> > +}
> > +#else
> > +#define	nfs_fattr_alloc(fattr, flags)
> > +#define	nfs_fattr_fini(fattr)
> > +#endif
> 
> Perhaps introduce a debug configuration option for this code.
> 
> 
> - James

A question about the debug configuration here. Exactly what information
are we looking to get for debugging. If we want line/file/function that
these are called on then I need a macro wrapper for the allocation as
well. If that is the case I'm guessing we always define the macros
nfs_fattr_alloc and nfs_fattr_fini and just make the internal functions
static inline so they can be compiled away when !CONFIG_SECURITY.

Dave

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