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

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Date:	Mon, 23 Nov 2009 02:10:21 -0800
From:	John Johansen <john.johansen@...onical.com>
To:	Eric Paris <eparis@...hat.com>
CC:	David Howells <dhowells@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	graff.yang@...il.com, linux-kernel@...r.kernel.org,
	gyang@...ckfin.uclinux.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	Graff Yang <graf.yang@...log.com>,
	linux-security-module@...r.kernel.org, john.johansen@...onical.com
Subject: Re: [PATCH] mm/nommu.c: Fix improperly call of security API in mmap

Eric Paris wrote:
> On Sat, 2009-11-21 at 00:16 +0000, David Howells wrote:
>> Eric Paris <eparis@...hat.com> wrote:
>>
>>> +/* sec_flags for security_file_mmap */
>>> +#define SECURITY_MMAP_ADDR_ONLY	0x01
>>> +#define SECURITY_MMAP_NOT_ADDR	0x02
>> Please add comments to these to indicate what they're intended to convey.
>> Would ADDR_ONLY be better as EXACT_ADDR?
> 
> I think I should point out that this hook checks 2 things.  Originally
> it was only used to check if a file should be allowed to be mmaped.  It
> was later enhanced to check if the return address of mmap, if it is file
> backed or anonymous, is acceptable.  These flags only influence the
> later.
> 
> ADDR_ONLY means the security system should only check the address.
> NOT_ADDR means they security system should not check the address.
> 
> You need ADDR_ONLY when the hook is called on map that is not file
> backed or where that has already been dealt with.  You need NOT_ADDR
> only for nommu where the whole idea of mmap_min_addr is pointless.
> 
> I'm not sure what comments would convey....
> 
> /* security hook should only check the address */
> #define SECURITY_MMAP_ADDR_ONLY	0x01
> /* security hook should not check the address */
> #define SECURITY_MMAP_NOT_ADDR	0x02
> 
> Does that add something?
> 
> Still haven't heard where people scream they absolutely need this today,
> so I'm going to ask James to carry it in his for-next tree.
> 
The comments convey a tad more but I don't think they are necessary, and
I concur, it would be good if it went into the for-next tree.

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