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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Fri, 2 Feb 2024 10:11:42 +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]

> > +
> > +static int pci_pwrctl_notify(struct notifier_block *nb, unsigned long action,
> > +                          void *data)
> > +{
> > +     struct pci_pwrctl *pwrctl = container_of(nb, struct pci_pwrctl, nb);
> > +     struct device *dev = data;
> > +
> > +     if (dev_fwnode(dev) != dev_fwnode(pwrctl->dev))
> > +             return NOTIFY_DONE;
> > +
> > +     switch (action) {
> > +     case BUS_NOTIFY_ADD_DEVICE:
> > +             device_set_of_node_from_dev(dev, pwrctl->dev);
>
> What happens if the bootloader left the power on, and the
> of_platform_populate() got probe deferred because the pwrseq wasn't
> ready, so this happens after pci_set_of_node() has been called?
>
> (I think dev->of_node will be put, then get and then node_reused
> assigned...but I'm not entirely sure)

That's exactly what will happen and the end result will be the same.

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

Yes, I'll address it.

> > +             break;
> > +     }
> > +
> > +     return NOTIFY_DONE;
> > +}
> > +
> > +int pci_pwrctl_device_enable(struct pci_pwrctl *pwrctl)
>
> This function doesn't really "enable the device", looking at the example
> driver it's rather "device_enabled" than "device_enable"...
>

I was also thinking about pci_pwrctl_device_ready() or
pci_pwrctl_device_prepared().

Bart

[snip!]