linux-kernel - Re: [PATCH] mm/nommu.c: Fix improperly call of security API in mmap

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Date:	Fri, 16 Oct 2009 16:43:10 +0100
From:	David Howells <dhowells@...hat.com>
To:	Eric Paris <eparis@...hat.com>
Cc:	dhowells@...hat.com, graff.yang@...il.com,
	linux-kernel@...r.kernel.org, gyang@...ckfin.uclinux.org,
	akpm@...ux-foundation.org, uclinux-dist-devel@...ckfin.uclinux.org,
	Graff Yang <graf.yang@...log.com>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] mm/nommu.c: Fix improperly call of security API in mmap

Eric Paris <eparis@...hat.com> wrote:

> That would still call cap_file_mmap() and wouldn't solve your problem.

Hmmm...  I guess I don't see the problem occur because I always run the
programs as root.

I would guess that cap_file_mmap() and selinux_file_mmap() are, perhaps, too
strict.  The hint shouldn't be rejected unless MAP_FIXED is also set, surely,
but should rather be revised upwards.

Certainly, addr==NULL and !MAP_FIXED is a reasonable case to permit, even in
tightly secured MMU and SELinux mode...  After all, the manual page says:

	If addr is NULL, then the kernel chooses the address at which to create
	the mapping; this is the most portable method of creating  a  new  map-
	ping.

David
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