linux-kernel - Re: Thoughts on credential switching

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Message-ID: <20140401212235.770843a0@alan.etchedpixels.co.uk>
Date:	Tue, 1 Apr 2014 21:22:35 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Jim Lieb <jlieb@...asas.com>, Jeff Layton <jlayton@...hat.com>,
	"Serge E. Hallyn" <serge@...onical.com>, bfields@...hat.com,
	"Theodore Ts'o" <tytso@....edu>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Kees Cook <keescook@...omium.org>
Subject: Re: Thoughts on credential switching

> Do we include credfd fds sitting in Unix sockets?

Ouch

> Hmm.  What if we had initial_creds and creds, and initial_creds never
> changed unless explicitly requested.  There wouldn't be any way to
> revert to initial_creds, but may_ptrace would check initial_creds
> *and* creds.  This is a little hacky, and it might break Android (I'm
> not really sure how the zygote thing works), but it could do the
> trick.

That mirros setfsuid and seteuid type behaviour so seems sensible enough.
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