linux-kernel - Re: [PATCH v3 1/3] msi: free msi_desc entry only after we've released the kobject

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Date:	Tue, 29 Oct 2013 07:32:35 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Veaceslav Falico <vfalico@...hat.com>
Cc:	linux-pci@...r.kernel.org, torvalds@...ux-foundation.org,
	tglx@...utronix.de, yinghai@...nel.org, Knut_Petersen@...nline.de,
	mingo@...nel.org, paulmck@...ux.vnet.ibm.com, fweisbec@...il.com,
	linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v3 1/3] msi: free msi_desc entry only after we've
 released the kobject

On Tue, Oct 29, 2013 at 11:30:30AM +0100, Veaceslav Falico wrote:
> Currently, we first do kobject_put(&entry->kobj) and the kfree(entry),
> however kobject_put() doesn't guarantee us that it was the last reference
> and that the kobj isn't used currently by someone else, so after we
> kfree(entry) with the struct kobject - other users will begin using the
> freed memory, instead of the actual kobject.
> 
> Fix this by using the kobject->release callback, which is called last when
> the kobject is indeed not used and is cleaned up - it's msi_kobj_release(),
> which can do the kfree(entry) safely (kobject_put/cleanup doesn't use the
> kobj itself after ->release() was called, so we're safe).
> 
> In case we've failed to create the sysfs directories - just kfree()
> it - cause we don't have the kobjects attached.
> 
> Also, remove the same functionality from populate_msi_sysfs(), cause on
> failure we anyway call free_msi_irqs(), which will take care of all the
> kobjects properly.
> 
> And add the forgotten pci_dev_put(pdev) in case of failure to register the
> kobject in populate_msi_sysfs().
> 
> CC: Bjorn Helgaas <bhelgaas@...gle.com>
> CC: Neil Horman <nhorman@...driver.com>
> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> CC: linux-pci@...r.kernel.org
> CC: linux-kernel@...r.kernel.org
> Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
Acked-by: Neil Horman <nhorman@...driver.com>

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