linux-kernel - Re: [PATCH] arm64: PCI: fix memleak when calling pci

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Message-ID: <20200907112118.GD26513@gaia>
Date:   Mon, 7 Sep 2020 12:21:19 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     George Cherian <gcherian@...vell.com>
Cc:     Yang Yingliang <yangyingliang@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "will.deacon@....com" <will.deacon@....com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "guohanjun@...wei.com" <guohanjun@...wei.com>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
Subject: Re: [PATCH] arm64: PCI: fix memleak when calling pci_iomap/unmap()

+ Lorenzo

On Mon, Sep 07, 2020 at 10:51:21AM +0000, George Cherian wrote:
> Catalin Marinas <catalin.marinas@....com> wrote:
> > On Sat, Sep 05, 2020 at 10:48:11AM +0800, Yang Yingliang wrote:
> > > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c index
> > > 1006ed2d7c604..ddfa1c53def48 100644
> > > --- a/arch/arm64/kernel/pci.c
> > > +++ b/arch/arm64/kernel/pci.c
> > > @@ -217,4 +217,9 @@ void pcibios_remove_bus(struct pci_bus *bus)
> > >  	acpi_pci_remove_bus(bus);
> > >  }
> > >
> > > +void pci_iounmap(struct pci_dev *dev, void __iomem *addr) {
> > > +	iounmap(addr);
> > > +}
> > > +EXPORT_SYMBOL(pci_iounmap);
> > 
> > So, what's wrong with the generic pci_iounmap() implementation?
> > Shouldn't it call iounmap() already?
> 
> Since ARM64 selects CONFIG_GENERIC_PCI_IOMAP and not
> CONFIG_GENERIC_IOMAP,  the pci_iounmap function is reduced to a NULL
> function. Due to this, even the managed release variants or even the explicit
> pci_iounmap calls doesn't really remove the mappings leading to leak.

Ah, I missed the fact that pci_iounmap() depends on a different
config option.

> https://lkml.org/lkml/2020/8/20/28

So is this going to be fixed in the generic code? That would be my
preference.

A problem with the iounmap() in the proposed patch is that the region
may have been an I/O port, so we could end up unmapping the I/O space.

-- 
Catalin