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

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Message-Id: <20110218155935.66e7782d.akpm@linux-foundation.org>
Date:	Fri, 18 Feb 2011 15:59:35 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	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

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...

>
> ...
>

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