linux-kernel - Re: [PATCH V8 3/5] PCI/ASPM: add init hook to device

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Date:   Thu, 13 Apr 2017 21:19:17 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     mayurkumar.patel@...el.com, David Daney <david.daney@...ium.com>,
        linux-pci@...r.kernel.org, timur@...eaurora.org,
        linux-kernel@...r.kernel.org, Julia Lawall <Julia.Lawall@...6.fr>,
        linux-arm-msm@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Rajat Jain <rajatja@...gle.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V8 3/5] PCI/ASPM: add init hook to device_add

On 4/13/2017 5:02 PM, Bjorn Helgaas wrote:
> I do see that you change the deallocation in patch [5/5], but I think
> the deallocation change should be in the same patch as the allocation
> change.  Otherwise I think we have a use-after-free problem in this
> sequence:

Sure, I'll reorder. As you can see here, link will be only removed if
root port is being removed.

Without this, we'll hit the use after free issue you mentioned.

	if (pdev->has_secondary_link) {
		link = pdev->link_state;
		down_read(&pci_bus_sem);
		mutex_lock(&aspm_lock);

		list_del(&link->sibling);
		list_del(&link->link);

		/* Clock PM is for endpoint device */
		free_link_state(link);
		mutex_unlock(&aspm_lock);
		up_read(&pci_bus_sem);
		return;
	}  

-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.