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Re: [RFC] fix race in drivers/char/random.c:get_reg()

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On Sun, Apr 30, 2017 at 9:49 AM, Michael Schmitz <schmitzmic@gmail.com> wrote:
> get_reg() can be reentered on architectures with prioritized interrupts
> (m68k in this case), causing f->reg_index to be incremented after the
> range check. Out of bounds memory access past the pt_regs struct results.
> This will go mostly undetected unless access is beyond end of memory.
>
> Prevent the race by disabling interrupts in get_reg().
>
> Tested on m68k (Atari Falcon, and ARAnyM emulator).
>
> Kudos to Geert Uytterhoeven for helping to trace this race.
>
> Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>

No comments from anyone?

Perhaps this wasn't clear, but (a) an access beyond end of memory crashes
the system, and (b) this is reproducible on Atari systems.

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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[RFC] fix race in drivers/char/random.c:get_reg() Michael Schmitz <schmitzmic@gmail.com> - 2017-04-30 09:50 +0200
  Re: [RFC] fix race in drivers/char/random.c:get_reg() Geert Uytterhoeven <geert@linux-m68k.org> - 2017-05-12 09:20 +0200
  Re: [RFC] fix race in drivers/char/random.c:get_reg() Theodore Ts'o <tytso@mit.edu> - 2017-05-24 23:50 +0200

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