RE: [PATCH] ACPI: scan: Fix a Hyper-V Linux VM panic caused by buffer overflow

[Dexuan Cui]

> From: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> Sent: Thursday, January 7, 2021 5:48 AM
> > > > Linux VM on Hyper-V crashes with the latest mainline:
> > > > ...
> The root cause is a VM issue AFAICS, though.

Yes.
 
> It doesn't look like the right fix to me, though.
> 
> The problem appears to be that the string coming from _HID is too long
> (which is a spec violation). 

Yes. We have requested Hyper-V team to fix the buggy BIOS/firmware,
but we have to cope with the existing buggy Hyper-V hosts, at least
before the Hyper-V fix is deployed to the hosts, and some old versions
of the hosts may not get updated. :-(

> The patch truncates it to match the
> length of the target buffer, but that is not particularly useful.
> 
> It would be better to use something like kstrdup_const() to initialize
> acpi_device_bus_id->bus_id IMV.

Makes sense. I'll submit v2 shortly.

Thanks,
-- Dexuan