linux-kernel - Re: [PATCH 08/23] PNPACPI: Fix device ref leaking in acpi_pnp

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Date:	Tue, 6 Mar 2012 20:53:50 -0700
From:	Bjorn Helgaas <bjorn.helgaas@...il.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>, x86 <x86@...nel.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...nel.org, Len Brown <lenb@...nel.org>,
	Adam Belay <abelay@....edu>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 08/23] PNPACPI: Fix device ref leaking in acpi_pnp_match

On Tue, Mar 6, 2012 at 12:13 AM, Yinghai Lu <yinghai@...nel.org> wrote:
> During testing pci root bus removal, found some root bus bridge is not freed.
>
> If booting with pnpacpi=off, those hostbridge could be freed without problem.
>
> It turns out that some devices reference are not released during acpi_pnp_match.
>
> that match should not hold one device ref during every calling.
>
> Add put_device calling before returning.
>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> Cc: stable@...nel.org
> Cc: Len Brown <lenb@...nel.org>
> Cc: Adam Belay <abelay@....edu>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: linux-acpi@...r.kernel.org
> ---
>  drivers/pnp/pnpacpi/core.c |    7 ++++++-
>  1 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/pnp/pnpacpi/core.c b/drivers/pnp/pnpacpi/core.c
> index b00c176..d21e8f5 100644
> --- a/drivers/pnp/pnpacpi/core.c
> +++ b/drivers/pnp/pnpacpi/core.c
> @@ -321,9 +321,14 @@ static int __init acpi_pnp_match(struct device *dev, void *_pnp)
>  {
>        struct acpi_device *acpi = to_acpi_device(dev);
>        struct pnp_dev *pnp = _pnp;
> +       struct device *physical_device;
> +
> +       physical_device = acpi_get_physical_device(acpi->handle);
> +       if (physical_device)
> +               put_device(physical_device);
>
>        /* true means it matched */
> -       return !acpi_get_physical_device(acpi->handle)
> +       return !physical_device
>            && compare_pnp_id(pnp->id, acpi_device_hid(acpi));
>  }
>

I spent about an hour convincing myself that this patch does the right
thing.  I *think* it does, but it certainly is not obvious.  It's
always nicer if the get/put are in the same function or in functions
that obviously correspond to each other.  But you didn't create this
mess, so I don't hold you responsible for fixing it :)

Bjorn
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