linux-kernel - Re: [PATCH 03/11] VFS: Add security label support to *notify

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Date:	Thu, 28 Feb 2008 12:20:30 +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 03/11] VFS: Add security label support to *notify

On Wed, 27 Feb 2008, David P. Quigley wrote:

> +int inode_setsecurity(struct inode *inode, struct iattr *attr)
> +{
> +	const char *suffix = security_maclabel_getname() 
> +				+ XATTR_SECURITY_PREFIX_LEN;
> +	int error;
> +
> +	if (!attr->ia_valid & ATTR_SECURITY_LABEL)
> +		return -EINVAL;

Do you mean:

	if (!(attr->ia_valid & ATTR_SECURITY_LABEL))

?

>  			mode &= ~S_ISGID;
>  		inode->i_mode = mode;
>  	}
> +#ifdef CONFIG_SECURITY
> +	if (ia_valid & ATTR_SECURITY_LABEL)
> +		inode_setsecurity(inode, attr);
> +#endif

You're not checking the return value of inode_setsecurity().

Why not just rely on inode_setsecurity() to perform the check, then you 
can lose the #ifdefs in the core code & make it a noop for 
!CONFIG_SECURITY.


> +#ifdef CONFIG_SECURITY
> +	if (ia_valid & ATTR_SECURITY_LABEL) {
> +		char *key = (char *)security_maclabel_getname();
> +		vfs_setxattr_locked(dentry, key,
> +			attr->ia_label, attr->ia_label_len, 0);
> +		/* Avoid calling inode_setsecurity()
> +		 * via inode_setattr() below
> +		 */
> +		attr->ia_valid &= ~ATTR_SECURITY_LABEL;
> +	}
> +#endif
> +

Similarly, make this a function which is compiled away for 
!CONFIG_SECURITY.

> +		if (!error) {
> +#ifdef CONFIG_SECURITY
> +			fsnotify_change(dentry, ATTR_SECURITY_LABEL);
> +#endif
>  			fsnotify_xattr(dentry);

Put the #ifdef inside fsnotify_change() and only process 
ATTR_SECURITY_LABEL if CONFIG_SECURITY.


> +#ifdef CONFIG_SECURITY
> +#define ATTR_SECURITY_LABEL  65536
> +#endif

I don't think there's any harm in always defining this.


-- 
James Morris
<jmorris@...ei.org>
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