linux-kernel - Re: [patch] vfs: make security_inode

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Date:	Wed, 30 Jul 2008 10:37:27 -0400
From:	Stephen Smalley <sds@...ho.nsa.gov>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	viro@...IV.linux.org.uk, akpm@...ux-foundation.org,
	jmorris@...ei.org, linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] vfs: make security_inode_setattr() calling consistent


On Wed, 2008-07-30 at 14:06 +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@...e.cz>
> 
> Call security_inode_setattr() consistetly before inode_change_ok().
> It doesn't make sense to try to "optimize" the i_op->setattr == NULL
> case, as most filesystem do define their own setattr function.
> 
> Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>

Unfortunate since we'd prefer to have the DAC checks applied first, and
since inode_change_ok() may alter the ia_mode in response to those
checks, but it does seem inconsistent at present and it doesn't yield
any difference in the ltp selinux testsuite results.

Acked-by:  Stephen Smalley <sds@...ho.nsa.gov>

> ---
>  fs/attr.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> Index: linux-2.6/fs/attr.c
> ===================================================================
> --- linux-2.6.orig/fs/attr.c	2008-07-30 13:52:35.000000000 +0200
> +++ linux-2.6/fs/attr.c	2008-07-30 13:52:41.000000000 +0200
> @@ -159,17 +159,17 @@ int notify_change(struct dentry * dentry
>  	if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
>  		return 0;
>  
> +	error = security_inode_setattr(dentry, attr);
> +	if (error)
> +		return error;
> +
>  	if (ia_valid & ATTR_SIZE)
>  		down_write(&dentry->d_inode->i_alloc_sem);
>  
>  	if (inode->i_op && inode->i_op->setattr) {
> -		error = security_inode_setattr(dentry, attr);
> -		if (!error)
> -			error = inode->i_op->setattr(dentry, attr);
> +		error = inode->i_op->setattr(dentry, attr);
>  	} else {
>  		error = inode_change_ok(inode, attr);
> -		if (!error)
> -			error = security_inode_setattr(dentry, attr);
>  		if (!error) {
>  			if ((ia_valid & ATTR_UID && attr->ia_uid != inode->i_uid) ||
>  			    (ia_valid & ATTR_GID && attr->ia_gid != inode->i_gid))
-- 
Stephen Smalley
National Security Agency

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