linux-kernel - Re: [PATCH] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT

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Date:   Thu, 13 Sep 2018 18:38:40 +0100
From:   Will Deacon <will.deacon@....com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     andrew.murray@....com,
        "zhichang.yuan" <yuanzhichang@...ilicon.com>,
        dann.frazier@...onical.com,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        jean-philippe.brucker@....com
Subject: Re: [PATCH] asm-generic: io: Fix ioport_map() for
 !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO

On Thu, Sep 13, 2018 at 04:00:54PM +0200, Arnd Bergmann wrote:
> On Thu, Sep 13, 2018 at 2:48 PM Andrew Murray <andrew.murray@....com> wrote:
> >
> > The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
> > prevent users from making I/O accesses outside the expected I/O range -
> > however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
> > contradictory to its other users.
> >
> > The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
> > amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
> > mangling the given port rather than capping it.
> >
> > We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
> > implementation of ioport_map by using the comparison operator and
> > returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
> > we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
> > we don't break existing buggy drivers that somehow rely on this masking.
> >
> > Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
> > Reported-by: Will Deacon <will.deacon@....com>
> > Signed-off-by: Andrew Murray <andrew.murray@....com>
> 
> Looks good to me,
> Reviewed-by: Arnd Bergmann <arnd@...db.de>
> 
> Can you take this through the arm64 tree?

Yup, I'll queue it up as a fix.

Cheers,

Will