[PATCH v1] mfd: core: Fix double-free in mfd_remove_devices_fn()

[PATCH v1] mfd: core: Fix double-free in mfd_remove_devices_fn()

[Dmitry Osipenko]

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@gmail.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;
 }
-- 
2.27.0

Re: [PATCH v1] mfd: core: Fix double-free in mfd_remove_devices_fn()

[Lee Jones]

On Tue, 18 Aug 2020, 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@gmail.com>
> ---
>  drivers/mfd/mfd-core.c | 2 --
>  1 file changed, 2 deletions(-)

Applied, thanks.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH v1] mfd: core: Fix double-free in mfd_remove_devices_fn()

[Marek Szyprowski]

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@gmail.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:

Reported-by: Marek Szyprowski <m.szyprowski@samsung.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
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH v1] mfd: core: Fix double-free in mfd_remove_devices_fn()

[Lee Jones]

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@gmail.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@samsung.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
Follow Linaro: Facebook | Twitter | Blog