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From: Roland McGrath <roland@hack.frob.com>
To: Eric Paris <eparis@parisplace.org>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
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Subject: Re: [PATCH 1/2] LSM: Do not apply mmap_min_addr check to PROT_NONE
 mappings
In-Reply-To: Eric Paris's message of  Monday, 24 October 2011 11:07:48 -0400 <1319468868.3280.9.camel@localhost>
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Emacs: the road to Hell is paved with extensibility.
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Date: Mon, 24 Oct 2011 09:28:42 -0700 (PDT)
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> I feel like, and it's just a very vague feeling, that the PROT bits
> didn't matter to the kernel.  It would still happily execute stuff on
> page 0 even without PROT_EXEC at some point in the past.  I'm probably
> totally off base, and I could test it, but I sort of feel like I
> remember something like that....

Saying that PROT_EXEC might not be enforced is quite a different thing than
saying "PROT bits don't matter".  It's certainly the case that in some past
kernel versions, some hardware (older x86 chips), some configurations (x86
non-PAE), and some modes (READ_IMPLIES_EXEC personality stuff), what you
can read, you can execute.  I sincerely doubt it's ever been the case that
anything mapped as PROT_NONE could be accessed in any manner.


Thanks,
Roland