linux-kernel - Re: [PATCH v2 1/3] PCI/sysfs: Fix null pointer dereference during hotplug

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Message-ID: <20251229173106.GA69373@bhelgaas>
Date: Mon, 29 Dec 2025 11:31:06 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Ziming Du <duziming2@...wei.com>
Cc: bhelgaas@...gle.com, jbarnes@...tuousgeek.org, chrisw@...hat.com,
	alex.williamson@...hat.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, liuyongqiang13@...wei.com
Subject: Re: [PATCH v2 1/3] PCI/sysfs: Fix null pointer dereference during
 hotplug

On Wed, Dec 24, 2025 at 05:27:17PM +0800, Ziming Du wrote:
> During the concurrent process of creating and rescanning in VF, the
> resource files for the same pci_dev may be created twice. The second
> creation attempt fails, resulting the res_attr in pci_dev to kfree(),
> but the pointer is not set to NULL. This will subsequently lead to
> dereferencing a null pointer when removing the device.
> 
> When we perform the following operation:
>   echo $vfcount > /sys/class/net/"$pfname"/device/sriov_numvfs &

Is the value of $vfcount relevant here?  Can you use the actual values
here instead of the variables so this is more useful to others?

>   sleep 0.5
>   echo 1 > /sys/bus/pci/rescan
>   pci_remove "$pfname"
> system will crash as follows: