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To:     Greg Kurz <groug@kaod.org>, linux-kernel@vger.kernel.org
From:   Michael Ellerman <patch-notifications@ellerman.id.au>
Cc:     Alexey Kardashevskiy <aik@ozlabs.ru>,
        linuxppc-dev@lists.ozlabs.org,
        Alistair Popple <alistair@popple.id.au>
Subject: Re: [PATCH] powerpc/powernv/npu: Fix reference leak
Message-Id: <45HZFp6yhxz9s7h@ozlabs.org>
Date:   Mon,  3 Jun 2019 22:32:46 +1000 (AEST)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, 2019-04-19 at 15:34:13 UTC, Greg Kurz wrote:
> Since 902bdc57451c, get_pci_dev() calls pci_get_domain_bus_and_slot(). This
> has the effect of incrementing the reference count of the PCI device, as
> explained in drivers/pci/search.c:
> 
>  * Given a PCI domain, bus, and slot/function number, the desired PCI
>  * device is located in the list of PCI devices. If the device is
>  * found, its reference count is increased and this function returns a
>  * pointer to its data structure.  The caller must decrement the
>  * reference count by calling pci_dev_put().  If no device is found,
>  * %NULL is returned.
> 
> Nothing was done to call pci_dev_put() and the reference count of GPU and
> NPU PCI devices rockets up.
> 
> A natural way to fix this would be to teach the callers about the change,
> so that they call pci_dev_put() when done with the pointer. This turns
> out to be quite intrusive, as it affects many paths in npu-dma.c,
> pci-ioda.c and vfio_pci_nvlink2.c. Also, the issue appeared in 4.16 and
> some affected code got moved around since then: it would be problematic
> to backport the fix to stable releases.
> 
> All that code never cared for reference counting anyway. Call pci_dev_put()
> from get_pci_dev() to revert to the previous behavior.
> 
> Fixes: 902bdc57451c ("powerpc/powernv/idoa: Remove unnecessary pcidev from pci_dn")
> Cc: stable@vger.kernel.org # v4.16
> Signed-off-by: Greg Kurz <groug@kaod.org>
> Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/02c5f5394918b9b47ff4357b1b183357

cheers