Re: [PATCH 1/2] PCI: Preserve the initial bus number in pci_dev

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] PCI: NULL pointer dereference in pci_alloc_dev() when bus is NULL
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commit 8257f74f7a4f8e2e670cc3291997e9d0a2cd7a56
Author: Mario Limonciello <mario.limonciello@amd.com>

PCI: Preserve the initial bus number in pci_dev

This commit adds an initial_bus_number field to struct pci_dev and populates
it during pci_alloc_dev() so drivers can match devices using their initial
firmware-visible bus number even after bus number reassignment.

> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 27008e2ea5afc..580b288d5c64f 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2508,6 +2508,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
>  	INIT_LIST_HEAD(&dev->bus_list);
>  	dev->dev.type = &pci_dev_type;
>  	dev->bus = pci_bus_get(bus);
> +	dev->initial_bus_number = bus->number;

[Severity: High]
Can bus be NULL here?

pci_bus_get() in drivers/pci/bus.c explicitly checks if bus is NULL before
dereferencing it:

struct pci_bus *pci_bus_get(struct pci_bus *bus)
{
	if (bus)
		get_device(&bus->dev);
	return bus;
}

There are also several in-tree callers that pass NULL to pci_alloc_dev(),
such as make_local_pdev() in drivers/scsi/megaraid.c, alpha_core_agp_setup()
in drivers/char/agp/alpha-agp.c, and parisc_agp_setup() in
drivers/char/agp/parisc-agp.c:

	*pdev = pci_alloc_dev(NULL);

Wouldn't dereferencing bus->number unconditionally in pci_alloc_dev() cause
a NULL pointer dereference for these callers?

>  	dev->driver_exclusive_resource = (struct resource) {
>  		.name = "PCI Exclusive",
>  		.start = 0,

[ ... ]

>
>

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Sashiko AI review · https://sashiko.dev/#/patchset/20261019-vfct-regression-v1-0-5a63ddd378dd@amd.com?part=1