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

Lee Jones
2019-11-26T13:50:14Z

On Mon, 25 Nov 2019, Lee Jones wrote:

> On Mon, 25 Nov 2019, Greg KH wrote:
>
> > On Mon, Nov 25, 2019 at 02:44:29PM +0000, Lee Jones wrote:
> > > 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.
> >
> > You have to look at others, we can't have regressions if people move
> > from one LTS to a newer one.

Okay, now sent appropriate patches to linux-4.14.y and linux-4.19.y.

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