linux-kernel - Re: [PATCH v3 3/4] lib: logic_pio: Reject accesses to unregistered CPU MMIO regions

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Date:   Thu, 4 Apr 2019 10:43:36 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     John Garry <john.garry@...wei.com>
Cc:     bhelgaas@...gle.com, rafael@...nel.org, arnd@...db.de,
        lorenzo.pieralisi@....com, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, bp@...e.de, wangkefeng.wang@...wei.com,
        linuxarm@...wei.com, andy.shevchenko@...il.com,
        linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
        will.deacon@....com
Subject: Re: [PATCH v3 3/4] lib: logic_pio: Reject accesses to unregistered
 CPU MMIO regions

On Thu, Apr 04, 2019 at 05:52:35PM +0100, John Garry wrote:
[ ... ]
> >>
> >>Note that the f71805f driver does not call request_{muxed_}region(), as it
> >>should.
> >>
> 
> Hi Guenter,
> 
> >... which is the real problem, one that is not solved by this patch. This may
> >result in parallel and descructive accesses if there is another device on the
> >LPC bus, and another driver accessing that device. Personally I'd rather have
> >request_muxed_region() added to the f71805f driver.
> 
> Right, we should and will still fix f71805f. If you recall, I did have the
> f71805f fix in the v1 series, but you committed that it was orthogonal, so I
> decided to take it out of this work for now.
> 
> And even if we fix up f71805f and other known drivers which don't call
> request_muxed_region(), we still need to police against these rogue
> accesses, which is what this patch attempts to do.
> 
Do we ? I am personally not convinced that LPC accesses _have_ to occur
through PCI on any given system.

I won't object to this series of patches - not my area. I do mind, though,
if one of the drivers I am responsible for is cited as reason or argument
for this series. I would prefer for those drivers to get fixed.

Guenter