[RFC][PATCHSET] VM_FAULT_RETRY fixes

[Geert Uytterhoeven]

Hi Mark,

On Wed, Feb 1, 2023 at 11:52 AM Mark Rutland <mark.rutland at arm.com> wrote:
> On Tue, Jan 31, 2023 at 08:02:51PM +0000, Al Viro wrote:
> > On x86 it had been noticed and fixed back in 2014, in 26178ec11ef3 "x86:
> > mm: consolidate VM_FAULT_RETRY handling".  Some of the other architectures
> > had it dealt with later - e.g. arm in 2017, the fix is 746a272e44141
> > "ARM: 8692/1: mm: abort uaccess retries upon fatal signal"; xtensa -
> > in 2021, the fix is 7b9acbb6aad4f "xtensa: fix uaccess-related livelock
> > in do_page_fault", etc.
> >
> > However, it never had been done on a bunch of architectures - the
> > current mainline still has that bug on alpha, hexagon, itanic, m68k,
> > microblaze, nios2, openrisc, parisc, riscv and sparc (both sparc32 and
> > sparc64).  Fixes are trivial, but I've no way to test them for most
> > of those architectures.
>
> FWIW, when I fixed arm and arm64 back in 2017, I did report the issue here with
> a test case (and again in 2021, with maintainers all explciitly Cc'd):
>
>   https://lore.kernel.org/lkml/20170822102527.GA14671@leverpostej/
>   https://lore.kernel.org/linux-arch/20210121123140.GD48431@C02TD0UTHF1T.local/
>
> ... so if anyone has access to those architectures, that test might be useful
> for verifying the fix.

Thanks a lot! This showed the problem on m68k, and confirmed Al's fix.

I'll give it a try on a few more systems later...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at 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