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Date: Tue, 01 Oct 2019 09:05:18 +0200
From: Florian Weimer <>
To: Rich Felker <>
Cc: Joshua Hudson <>,
Subject: Re: Re: posix_spawn

* Rich Felker:

> This is not safe and creates a false sense that something broken might
> work. Moreover it's a vulnerability to use it this way. You have a
> window where different tasks sharing VM space are executing with
> different privilege levels, and thereby one is able to seize execution
> of the other and achieve its privilege level.

That's a non-sequitur.  A shared address space does not necessarily mean
that execution under one set of credentials will have unrestricted
effects on executions under different credentials within the same
address space.  If the executions themselves are constrained, this can
be completely safe.  It is true that if there is one unconstrained
execution in an address space, then the whole thing is tainted, but that
this isn't the relevant scenario for things like file servers (which do
not execute code on behalf of clients).

I don't know where you got this idea, but it is wrong.  I'm sorry.

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