linux-kernel - Re: [PATCH v1] mfd: core: Fix double-free in mfd_remove_devices

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Date:   Mon, 24 Aug 2020 09:49:35 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Dmitry Osipenko <digetx@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] mfd: core: Fix double-free in mfd_remove_devices_fn()

On Mon, 24 Aug 2020, Marek Szyprowski wrote:

> Hi
> 
> On 18.08.2020 01:50, Dmitry Osipenko wrote:
> > The pdev.mfd_cell is released by platform_device_release(), which is
> > invoked by platform_device_unregister(). Hence mfd_remove_devices_fn()
> > shouldn't release the cell variable. The double-free bug is reported KASAN
> > during of MFD driver module removal.
> >
> > Fixes: 466a62d7642f ("mfd: core: Make a best effort attempt to match devices with the correct of_nodes")
> > Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> > ---
> 
> I've reported that almost a week earlier and got information that it 
> will be dropped:
> 
> https://lore.kernel.org/lkml/79bcd1b5-2247-5e00-7d49-2f94f9b40744@samsung.com/
> 
> https://lore.kernel.org/lkml/20200813080100.GI4354@dell/
> 
> Sadly it finally landed in v5.9-rc1. Would be nice to mention this in 
> the revert:

That's true.  The patch was taken out but the change managed to get in
via another commit.  I will add your Reported-by to the revert.

> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> 
> >   drivers/mfd/mfd-core.c | 2 --
> >   1 file changed, 2 deletions(-)
> >
> > diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> > index c3651f06684f..c50718e3db58 100644
> > --- a/drivers/mfd/mfd-core.c
> > +++ b/drivers/mfd/mfd-core.c
> > @@ -370,8 +370,6 @@ static int mfd_remove_devices_fn(struct device *dev, void *data)
> >   	regulator_bulk_unregister_supply_alias(dev, cell->parent_supplies,
> >   					       cell->num_parent_supplies);
> >   
> > -	kfree(cell);
> > -
> >   	platform_device_unregister(pdev);
> >   	return 0;
> >   }
> 
> Best regards

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