linux-kernel - Re: [PATCH 1/6] user namespace: make signal.c respect user namespaces (v4)

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Message-Id: <20111108162216.1ffb3e9a.akpm@linux-foundation.org>
Date:	Tue, 8 Nov 2011 16:22:16 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Serge Hallyn <serge@...lyn.com>
Cc:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, oleg@...hat.com,
	richard@....at, ebiederm@...ssion.com, dhowells@...hat.com,
	eparis@...hat.com, Serge Hallyn <serge.hallyn@...onical.com>
Subject: Re: [PATCH 1/6] user namespace: make signal.c respect user
 namespaces (v4)

On Fri,  4 Nov 2011 22:24:37 +0000
Serge Hallyn <serge@...lyn.com> wrote:

> +static inline void fixup_uid(struct siginfo *info, struct task_struct *t)
> +{
> +#ifdef CONFIG_USER_NS
> +	if (current_user_ns() == task_cred_xxx(t, user_ns))
> +#endif
> +		return;
> +
> +	if (SI_FROMKERNEL(info))
> +		return;
> +
> +	info->si_uid = user_ns_map_uid(task_cred_xxx(t, user_ns),
> +					current_cred(), info->si_uid);
> +}

err, this function is a no-op if CONFIG_USER_NS=n.  If that was
intentional then why on earth do this in such a weird fashion?  If
unintentional then it makes me wonder how well tested all this was with
CONFIG_USER_NS=n?

I vaguely remember that I've forgotten how all this stuff works.  Some
additional review input would be nice (cough-oleg-cough).

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