[GHC] #14069: RTS linker maps code as writable

[GHC]

#14069: RTS linker maps code as writable
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        Reporter:  bgamari           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Runtime System    |              Version:  8.0.1
  (Linker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Description changed by bgamari:

Old description:

> GHC's RTS linker maps executable code in writable pages, representing a
> significant potential exploit point for arbitrary code execution. OpenBSD
> disallows running program that do this by default.
>
> Fix this.

New description:

 GHC's RTS linker maps executable code in writable pages, representing a
 significant potential exploit point for arbitrary code execution. OpenBSD
 disallows running program that do this by default.


 Instead we should first map pages as `PROT_READ | PROT_WRITE`, perform any
 necessary relocations (which requires writing), and then `mprotect` it to
 `PROT_READ | PROT_EXEC`.

 To find the relevant code grep for `PROT_EXEC` in the `rts/` directory.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14069#comment:1>
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