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Date: Thu, 10 Mar 2016 15:20:50 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Memory management, how to protect some address space.

On Thu, Mar 10, 2016 at 09:23:02PM +0200, John Found wrote:
> On Thu, 10 Mar 2016 14:11:03 -0500
> Rich Felker <dalias@...c.org> wrote:
> 
> > The proper way to use personality() is before exec'ing your program.
> > The stack address and some spare memory that musl re-uses as heap get
> > assigned at exec time before you can do anything within your program
> > to prevent that from happening. In theory that could happen with glibc
> > too; if it doesn't you're just getting lucky.
> > 
> > Rich
> 
> Hm, isn't it paragraph 22? sys_personality changes the personality
> of the calling process.
> How to call it *before* executing program???

exec does not make a new process; it replaces the program running in
the current process with a new one. There's actually a command line
too (I forget the name) to run a program with a particular personality
that calls personality() before execve().

Rich

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