Re: Executing from dynamically allocated memory

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From	sandmann@cs.au.dk (Søren Sandmann)
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Subject	Re: Executing from dynamically allocated memory
Date	Sat, 12 Oct 2013 20:58:42 +0200
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"news" <news@fx32.iad.highwinds-media.com> writes:

> In the past, I've malloc'd memory, written machine instructions into it,
> and called the function I built there.
>
> All this on a 32-bit intel instruction set, on a Debian system.
>
> This appears no longer too work.  My program gives a segmentation fault.
> The debugger tells me that the segmentation fault occurs on the first
> instruction of the called function, a
> 	push   %ebp
> residing in malloced memory.
>
> Now it was a year or three ago that this worked.  Has Linux changed in
> this respect?  Is there something new I have to do to allocate executable
> writable memory for this purpose?
>
> Or might there be something even weirder going on?

It's probably just that anonymous memory is not executable by default
anymore. Take a look at this:

    http://www.akkadia.org/drepper/selinux-mem.html

in particular the execmem case. There is also example code.

SC8ren

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Executing from dynamically allocated memory "news" <news@fx32.iad.highwinds-media.com> - 2013-10-12 00:05 +0000
  Re: Executing from dynamically allocated memory "James Harris" <james.harris.1@gmail.com> - 2013-10-12 10:10 +0100
  Re: Executing from dynamically allocated memory Sébastien Fricker <sebastien.fricker@gmail.com> - 2013-10-12 11:52 +0200
  Re: Executing from dynamically allocated memory chakaram@auth.gr - 2013-10-12 19:20 +0300
  Re: Executing from dynamically allocated memory Alex McDonald <blog@rivadpm.com> - 2013-10-12 11:12 -0700
  Re: Executing from dynamically allocated memory sandmann@cs.au.dk (Søren Sandmann) - 2013-10-12 20:58 +0200
  Re: Executing from dynamically allocated memory Jens Kallup <jkallup@web.de> - 2013-10-13 10:44 +0200

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