Re: [patch] remove MNT_NOEXEC check for PROT_EXEC mmaps

From: David Wagner
Date: Sun Sep 24 2006 - 15:14:47 EST

Stas Sergeev wrote:
>Ulrich Drepper wrote:
>> The consensus has been to add the same checks to mprotect. They were
>> not left out intentionally.
>But how about the anonymous mmap with PROT_EXEC set?

I'm curious about this, too. is a purely unprivileged
program. It isn't setuid root. Can you write a variant of
that reads an executable into memory off of a partition mounted noexec and
then begins executing that code? (perhaps by using anonymous mmap with
PROT_EXEC or some other mechanism) It sure seems like the answer would
be yes. If so, I'm having a hard time understanding what guarantees
noexec gives you. Isn't the noexec flag just a speedbump that raises
the bar a little but doesn't really prevent anything?
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