linux-kernel - Re: [PATCH v7 2/6] ocfs2: Switch to security_inode_init

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Date:   Mon, 20 Feb 2023 13:20:56 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, mark@...heh.com,
        jlbec@...lplan.org, joseph.qi@...ux.alibaba.com,
        dmitry.kasatkin@...il.com, paul@...l-moore.com, jmorris@...ei.org,
        serge@...lyn.com, stephen.smalley.work@...il.com,
        eparis@...isplace.org, casey@...aufler-ca.com
Cc:     ocfs2-devel@....oracle.com, reiserfs-devel@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org, keescook@...omium.org,
        nicolas.bouchinet@...p-os.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v7 2/6] ocfs2: Switch to security_inode_init_security()

On Mon, 2023-02-20 at 06:08 -0500, Mimi Zohar wrote:
> > > > > diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> > > > > index 95d0611c5fc7..55699c573541 100644
> > > > > @@ -7277,13 +7289,23 @@ int ocfs2_init_security_get(struct inode *inode,
> > > > >  			    const struct qstr *qstr,
> > > > >  			    struct ocfs2_security_xattr_info *si)
> > > > >  {
> > > > > +	int ret;
> > > > > +
> > > > >  	/* check whether ocfs2 support feature xattr */
> > > > >  	if (!ocfs2_supports_xattr(OCFS2_SB(dir->i_sb)))
> > > > >  		return -EOPNOTSUPP;
> > > > > -	if (si)
> > > > > -		return security_old_inode_init_security(inode, dir, qstr,
> > > > > -							&si->name, &si->value,
> > > > > -							&si->value_len);
> > > > > +	if (si) {
> > > > > +		ret = security_inode_init_security(inode, dir, qstr,
> > > > > +						   &ocfs2_initxattrs, si);
> > > > 
> > > > The "if (unlikely(IS_PRIVATE(inode))"  test exists in both
> > > > security_old_inode_init_security() and security_inode_init_security(),
> > > > but return different values.  In the former case, it returns
> > > > -EOPNOTSUPP.  In the latter case, it returns 0.  The question is
> > > > whether or not we need to be concerned about private inodes on ocfs2.  
> > > > If private inodes on ocfs2 are possible, then ocsf2_mknod() or
> > > > ocfs2_symlink() would fail to create the inode or symlink.
> > > 
> > > Correction, previously when returning -EOPNOTSUPP for private inodes,
> > > xattrs would not be wrriten.  By returning 0 without setting si->enable 
> > > to 0, xattrs will be written.
> > 
> > Ok, but if there is a private inode, we would be setting si->enable to
> > zero. Should be ok, I guess.
> 
> si->enable is being set to zero, below, but is conditional on !si-
> > name.
> 
> This is the last concern, otherwise the patch set looks good.

Uhm, if the inode is private, security_inode_init_security() will
immediately return. So, the condition !si->name should be always true.

Thanks

Roberto

> > > > > +		/*
> > > > > +		 * security_inode_init_security() does not return -EOPNOTSUPP,
> > > > > +		 * we have to check the xattr ourselves.
> > > > > +		 */
> > > > > +		if (!ret && !si->name)
> > > > > +			si->enable = 0;
> > > > > +
> > > > > +		return ret;
> > > > > +	}
> > > > >  
> > > > >  	return security_inode_init_security(inode, dir, qstr,
> > > > >  					    &ocfs2_initxattrs, NULL);