linux-kernel - Re: [RFC 8/9] PCI/pwrctl: add PCI power control core code

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Date: Wed, 14 Feb 2024 16:46:25 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Bjorn Andersson <andersson@...nel.org>
Cc: Konrad Dybcio <konrad.dybcio@...aro.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Marcel Holtmann <marcel@...tmann.org>, Luiz Augusto von Dentz <luiz.dentz@...il.com>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Alex Elder <elder@...aro.org>, Srini Kandagatla <srinivas.kandagatla@...aro.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arnd Bergmann <arnd@...db.de>, 
	Abel Vesa <abel.vesa@...aro.org>, Manivannan Sadhasivam <mani@...nel.org>, Lukas Wunner <lukas@...ner.de>, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org, 
	linux-pci@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [RFC 8/9] PCI/pwrctl: add PCI power control core code

On Fri, Feb 2, 2024 at 4:53 AM Bjorn Andersson <andersson@...nel.org> wrote:
>

[snip]

>
> > +             break;
> > +     case BUS_NOTIFY_BOUND_DRIVER:
> > +             pwrctl->link = device_link_add(dev, pwrctl->dev,
> > +                                            DL_FLAG_AUTOREMOVE_CONSUMER);
> > +             if (!pwrctl->link)
> > +                     dev_err(pwrctl->dev, "Failed to add device link\n");
> > +             break;
> > +     case BUS_NOTIFY_UNBOUND_DRIVER:
> > +             device_link_del(pwrctl->link);
>
> This might however become a NULL-pointer dereference, if dev was bound
> to its driver before the pci_pwrctl_notify() was registered for the
> pwrctl and then the PCI device is unbound.
>

Right. And it also makes me think that right after registering with
the notifier, we should iterate over the PCI bus devices and see if
the relevant one is already there.

> This would also happen if device_link_add() failed when the PCI device
> was bound...
>

Right.

Bart

[snip]