linux-kernel - Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks

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Date:	Thu, 24 Feb 2011 03:24:16 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	LSM <linux-security-module@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	Kees Cook <kees.cook@...onical.com>,
	containers@...ts.linux-foundation.org,
	kernel list <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michael Kerrisk <mtk.manpages@...il.com>, xemul@...allels.com,
	dhowells@...hat.com
Subject: Re: [PATCH 9/9] userns: check user namespace for task->file uid
 equivalence checks

Quoting Andrew Morton (akpm@...ux-foundation.org):
> On Thu, 17 Feb 2011 15:04:07 +0000
> "Serge E. Hallyn" <serge@...lyn.com> wrote:
> 
> > Cheat for now and say all files belong to init_user_ns.  Next
> > step will be to let superblocks belong to a user_ns, and derive
> > inode_userns(inode) from inode->i_sb->s_user_ns.  Finally we'll
> > introduce more flexible arrangements.
> > 
> >
> > ...
> >
> > +
> > +/*
> > + * return 1 if current either has CAP_FOWNER to the
> > + * file, or owns the file.
> > + */
> > +int is_owner_or_cap(const struct inode *inode)
> > +{
> > +	struct user_namespace *ns = inode_userns(inode);
> > +
> > +	if (current_user_ns() == ns && current_fsuid() == inode->i_uid)
> > +		return 1;
> > +	if (ns_capable(ns, CAP_FOWNER))
> > +		return 1;
> > +	return 0;
> > +}
> 
> bool?
> 
> > +EXPORT_SYMBOL(is_owner_or_cap);
> 
> There's a fairly well adhered to convention that global symbols (and
> often static symbols) have a prefix which identifies the subsystem to
> which they belong.  This patchset rather scorns that convention.
> 
> Most of these identifiers are pretty obviously from the capability
> subsystem, but still...

Would 'inode_owner_or_capable' be better and and make sense?

-serge
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