linux-kernel - Re: [PATCH 2/2] PCI: Fix double free in pci_register_host

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Message-ID: <20250307195033.GA424012@bhelgaas>
Date: Fri, 7 Mar 2025 13:50:33 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Ma Ke <make24@...as.ac.cn>, Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] PCI: Fix double free in pci_register_host_bridge()

On Fri, Mar 07, 2025 at 11:46:41AM +0300, Dan Carpenter wrote:
> Calling put_device(&bus->dev) will call release_pcibus_dev() which will
> free the bus.  It leads to a use after free when we dereference "bus" in
> the cleanup code and the kfree(bus) is a double free.
> 
> Fixes: b80b4d4972e6 ("PCI: Fix reference leak in pci_register_host_bridge()")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>

Squashed into the b80b4d4972e6 commit on pci/enumeration for v6.15,
thanks!

> ---
>  drivers/pci/probe.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 819d23ce3565..c13f2c957002 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -957,6 +957,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>  	resource_size_t offset, next_offset;
>  	LIST_HEAD(resources);
>  	struct resource *res, *next_res;
> +	bool bus_registered = false;
>  	char addr[64], *fmt;
>  	const char *name;
>  	int err;
> @@ -1020,10 +1021,9 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>  	name = dev_name(&bus->dev);
>  
>  	err = device_register(&bus->dev);
> -	if (err) {
> -		put_device(&bus->dev);
> +	bus_registered = true;
> +	if (err)
>  		goto unregister;
> -	}
>  
>  	pcibios_add_bus(bus);
>  
> @@ -1110,12 +1110,15 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>  unregister:
>  	put_device(&bridge->dev);
>  	device_del(&bridge->dev);
> -
>  free:
>  #ifdef CONFIG_PCI_DOMAINS_GENERIC
>  	pci_bus_release_domain_nr(parent, bus->domain_nr);
>  #endif
> -	kfree(bus);
> +	if (bus_registered)
> +		put_device(&bus->dev);
> +	else
> +		kfree(bus);
> +
>  	return err;
>  }
>  
> -- 
> 2.47.2
>