linux-kernel - Re: [patch] remove MNT_NOEXEC check for PROT

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Message-ID: <efvcs7$526$1@taverner.cs.berkeley.edu>
Date:	Wed, 4 Oct 2006 04:21:27 +0000 (UTC)
From:	daw@...berkeley.edu (David Wagner)
To:	linux-kernel@...r.kernel.org
Subject: Re: [patch] remove MNT_NOEXEC check for PROT_EXEC mmaps

Ulrich Drepper wrote:
>On 10/3/06, David Wagner <daw@...berkeley.edu> wrote:
>> Are you familiar with the mmap(PROT_EXEC, MAP_ANONYMOUS) loophole?
>
>Another person who doesn't know about SELinux.  Read
>
>http://people.redhat.com/drepper/selinux-mem.html

You're right, I didn't know about that one.  Thanks for the
education and for taking the time to respond.

I wonder whether it is feasible to run with allow_exec{heap,mem,mod,stack}
all set to false, on a real system.  Is there any example of a fully
worked out SELinux policy that has these set to false?  FC5 has
allow_execheap set to false and all others set to true in its default
SELinux policy, so it looks like the mmap(PROT_EXEC, MAP_ANONYMOUS)
loophole remains open in FC5 by default.  My concern would be that setting
all of the exec-related booleans to false might break so much code that
setting them all to false wouldn't be feasible in practice.  If so,
the theoretical possibility to close the mmap(PROT_EXEC, MAP_ANONYMOUS)
loophole may be one of these things that is possible in theory but not
in practice.
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