linux-kernel - Re: [patch] unprivileged mounts update

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Message-Id: <E1HgnFH-0006gR-00@dorka.pomaz.szeredi.hu>
Date:	Wed, 25 Apr 2007 21:33:43 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	serge@...lyn.com
CC:	ebiederm@...ssion.com, hpa@...or.com, miklos@...redi.hu,
	akpm@...ux-foundation.org, viro@....linux.org.uk,
	linuxram@...ibm.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, containers@...ts.osdl.org,
	linux-security-module@...r.kernel.org
Subject: Re: [patch] unprivileged mounts update

> Right, I figure if the normal action is to always do
> mnt->user = current->fsuid, then for the special case we
> pass a uid in someplace.  Of course...  do we not have a
> place to do that?  Would it be a no-no to use 'data' for
> a non-fs-specific arg?

I guess it would be OK for bind, but not for new- and remounts, where
'data' is already used.

Maybe it's best to stay with fsuid after all, and live with having to
restore capabilities.  It's not so bad after all, this seems to do the
trick:

	cap_t cap = cap_get_proc();
	setfsuid(uid);
	cap_set_proc(cap);

Unfortunately these functions are not in libc, but in a separate
"libcap" library.  Ugh.

Miklos
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