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

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Date:	Thu, 28 Feb 2008 12:04:49 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	"David P. Quigley" <dpquigl@...ho.nsa.gov>
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 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
-- 
James Morris
<jmorris@...ei.org>
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