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

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Message-ID: <45240BF0.4050400@aknet.ru>
Date:	Wed, 04 Oct 2006 23:30:56 +0400
From:	Stas Sergeev <stsp@...et.ru>
To:	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch] remove MNT_NOEXEC check for PROT_EXEC mmaps

Hello.

David Wagner wrote:
>>/That's obviously possible, but I'd feel safer having/
>>/"noexec" on *every* user-writable partition./
> But why would you "feel" safer?  And why should the Linux kernel care
> about how people "feel"?
I am more wondering why should I answer this,
esp. since you do not even care to CC me.

> What threat, exactly, are you trying to
> defend against?  What's your threat model?
Am I supposed to explain why I want to prevent an
attacker from executing the exploit he happened to
copy to one of the user-writable mounts of mine?

> so you say it is not a library and not a binary.  So what is it that you
> are maping in as executable, and why do you think it is reasonable to
> ask the Linux kernel to allow you to execute it, if it lives on a noexec
> partition?
Quick answer is: because not having the exec permission
(chmod -x file) doesn't prevent you from mapping that
file "noexec", and that's correct, not bug. The more
detailed discussion have already happened, and I'd like
to leave MAP_SHARED aside for a time.
Please tell me how your logic applies to MAP_PRIVATE instead,
because right now MAP_PRIVATE is affected the same way the
MAP_SHARED is.

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