Re: [PATCH 4.9 3/8] arm64: fix for bad_mode() handler to always result in panic

Lee Jones
2019-11-25T14:44:50Z

On Mon, 25 Nov 2019, Sasha Levin wrote:

> On Fri, Nov 22, 2019 at 10:52:48AM +0000, Lee Jones wrote:
> > From: Hari Vyas <hari.vyas@broadcom.com>
> >
> > [ Upstream commit e4ba15debcfd27f60d43da940a58108783bff2a6 ]
> >
> > The bad_mode() handler is called if we encounter an uunknown exception,
> > with the expectation that the subsequent call to panic() will halt the
> > system. Unfortunately, if the exception calling bad_mode() is taken from
> > EL0, then the call to die() can end up killing the current user task and
> > calling schedule() instead of falling through to panic().
> >
> > Remove the die() call altogether, since we really want to bring down the
> > machine in this "impossible" case.
>
> Should this be in newer LTS kernels too? I don't see it in 4.14. We
> can't take anything into older kernels if it's not in newer ones - we
> don't want to break users who update their kernels.

Only; 3.18, 4.4, 4.9 and 5.3 were studied.

I can look at others if it helps.

--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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