| From | Geert Uytterhoeven <> | Date | Tue, 20 Mar 2018 10:48:48 +0100 | Subject | Re: [PATCH AUTOSEL for 3.18 044/102] fix race in drivers/char/random.c:get_reg() |
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Hi Sasha,
On Mon, Mar 19, 2018 at 5:12 PM, Sasha Levin <Alexander.Levin@microsoft.com> wrote: > From: Michael Schmitz <schmitzmic@gmail.com> > > [ Upstream commit 9dfa7bba35ac08a63565d58c454dccb7e1bb0a08 ] > > 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> > Signed-off-by: Theodore Ts'o <tytso@mit.edu> > Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
You probably want to apply follow-up commit 92e75428ffc90e2a ("random: use lockless method of accessing and updating f->reg_idx"), too.
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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