linux-kernel - Re: [PATCH] PCI: take the rescan lock when adding devices during host probe

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Message-ID: <20241001211102.GA227022@bhelgaas>
Date: Tue, 1 Oct 2024 16:11:02 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH] PCI: take the rescan lock when adding devices during
 host probe

On Thu, Sep 26, 2024 at 03:09:23PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> Since adding the PCI power control code, we may end up with a race
> between the pwrctl platform device rescanning the bus and the host
> controller probe function. The latter needs to take the rescan lock when
> adding devices or may crash.
> 
> Reported-by: Konrad Dybcio <konradybcio@...nel.org>
> Fixes: 4565d2652a37 ("PCI/pwrctl: Add PCI power control core code")
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---
>  drivers/pci/probe.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 4f68414c3086..f1615805f5b0 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -3105,7 +3105,9 @@ int pci_host_probe(struct pci_host_bridge *bridge)
>  	list_for_each_entry(child, &bus->children, node)
>  		pcie_bus_configure_settings(child);
>  
> +	pci_lock_rescan_remove();
>  	pci_bus_add_devices(bus);
> +	pci_unlock_rescan_remove();

Seems like we do need locking here, but don't we need a more
comprehensive change?  There are many other callers of
pci_bus_add_devices(), and most of them look similarly unprotected.

>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(pci_host_probe);
> -- 
> 2.30.2
>