Re: [PATCH 05/12] PCI: use generic driver_override infrastructure

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Mar 24, 2026 at 01:59:09AM +0100, Danilo Krummrich wrote:
> When a driver is probed through __driver_attach(), the bus' match()
> callback is called without the device lock held, thus accessing the
> driver_override field without a lock, which can cause a UAF.
> 
> Fix this by using the driver-core driver_override infrastructure taking
> care of proper locking internally.
> 
> Note that calling match() from __driver_attach() without the device lock
> held is intentional. [1]
> 
> Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [1]
> Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
> Fixes: 782a985d7af2 ("PCI: Introduce new device binding path using pci_dev.driver_override")
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  drivers/pci/pci-driver.c           | 11 +++++++----
>  drivers/pci/pci-sysfs.c            | 28 ----------------------------
>  drivers/pci/probe.c                |  1 -
>  include/linux/pci.h                |  6 ------

For the above:

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

"driver_override" is mentioned several places in
Documentation/ABI/testing/sysfs-bus-*.  I assume this series doesn't
change the behavior documented there?  Should any of this doc be
consolidated?

>  drivers/vfio/pci/vfio_pci_core.c   |  5 ++---
>  drivers/xen/xen-pciback/pci_stub.c |  6 ++++--
>  6 files changed, 13 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index dd9075403987..d10ece0889f0 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -138,9 +138,11 @@ static const struct pci_device_id *pci_match_device(struct pci_driver *drv,
>  {
>  	struct pci_dynid *dynid;
>  	const struct pci_device_id *found_id = NULL, *ids;
> +	int ret;
>  
>  	/* When driver_override is set, only bind to the matching driver */
> -	if (dev->driver_override && strcmp(dev->driver_override, drv->name))
> +	ret = device_match_driver_override(&dev->dev, &drv->driver);
> +	if (ret == 0)
>  		return NULL;
>  
>  	/* Look at the dynamic ids first, before the static ones */
> @@ -164,7 +166,7 @@ static const struct pci_device_id *pci_match_device(struct pci_driver *drv,
>  		 * matching.
>  		 */
>  		if (found_id->override_only) {
> -			if (dev->driver_override)
> +			if (ret > 0)
>  				return found_id;
>  		} else {
>  			return found_id;
> @@ -172,7 +174,7 @@ static const struct pci_device_id *pci_match_device(struct pci_driver *drv,
>  	}
>  
>  	/* driver_override will always match, send a dummy id */
> -	if (dev->driver_override)
> +	if (ret > 0)
>  		return &pci_device_id_any;
>  	return NULL;
>  }
> @@ -452,7 +454,7 @@ static int __pci_device_probe(struct pci_driver *drv, struct pci_dev *pci_dev)
>  static inline bool pci_device_can_probe(struct pci_dev *pdev)
>  {
>  	return (!pdev->is_virtfn || pdev->physfn->sriov->drivers_autoprobe ||
> -		pdev->driver_override);
> +		device_has_driver_override(&pdev->dev));
>  }
>  #else
>  static inline bool pci_device_can_probe(struct pci_dev *pdev)
> @@ -1722,6 +1724,7 @@ static const struct cpumask *pci_device_irq_get_affinity(struct device *dev,
>  
>  const struct bus_type pci_bus_type = {
>  	.name		= "pci",
> +	.driver_override = true,
>  	.match		= pci_bus_match,
>  	.uevent		= pci_uevent,
>  	.probe		= pci_device_probe,
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 16eaaf749ba9..a9006cf4e9c8 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -615,33 +615,6 @@ static ssize_t devspec_show(struct device *dev,
>  static DEVICE_ATTR_RO(devspec);
>  #endif
>  
> -static ssize_t driver_override_store(struct device *dev,
> -				     struct device_attribute *attr,
> -				     const char *buf, size_t count)
> -{
> -	struct pci_dev *pdev = to_pci_dev(dev);
> -	int ret;
> -
> -	ret = driver_set_override(dev, &pdev->driver_override, buf, count);
> -	if (ret)
> -		return ret;
> -
> -	return count;
> -}
> -
> -static ssize_t driver_override_show(struct device *dev,
> -				    struct device_attribute *attr, char *buf)
> -{
> -	struct pci_dev *pdev = to_pci_dev(dev);
> -	ssize_t len;
> -
> -	device_lock(dev);
> -	len = sysfs_emit(buf, "%s\n", pdev->driver_override);
> -	device_unlock(dev);
> -	return len;
> -}
> -static DEVICE_ATTR_RW(driver_override);
> -
>  static struct attribute *pci_dev_attrs[] = {
>  	&dev_attr_power_state.attr,
>  	&dev_attr_resource.attr,
> @@ -669,7 +642,6 @@ static struct attribute *pci_dev_attrs[] = {
>  #ifdef CONFIG_OF
>  	&dev_attr_devspec.attr,
>  #endif
> -	&dev_attr_driver_override.attr,
>  	&dev_attr_ari_enabled.attr,
>  	NULL,
>  };
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index bccc7a4bdd79..b4707640e102 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2488,7 +2488,6 @@ static void pci_release_dev(struct device *dev)
>  	pci_release_of_node(pci_dev);
>  	pcibios_release_device(pci_dev);
>  	pci_bus_put(pci_dev->bus);
> -	kfree(pci_dev->driver_override);
>  	bitmap_free(pci_dev->dma_alias_mask);
>  	dev_dbg(dev, "device released\n");
>  	kfree(pci_dev);
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index d43745fe4c84..460852f79f29 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1987,9 +1987,8 @@ static int vfio_pci_bus_notifier(struct notifier_block *nb,
>  	    pdev->is_virtfn && physfn == vdev->pdev) {
>  		pci_info(vdev->pdev, "Captured SR-IOV VF %s driver_override\n",
>  			 pci_name(pdev));
> -		pdev->driver_override = kasprintf(GFP_KERNEL, "%s",
> -						  vdev->vdev.ops->name);
> -		WARN_ON(!pdev->driver_override);
> +		WARN_ON(device_set_driver_override(&pdev->dev,
> +						   vdev->vdev.ops->name));
>  	} else if (action == BUS_NOTIFY_BOUND_DRIVER &&
>  		   pdev->is_virtfn && physfn == vdev->pdev) {
>  		struct pci_driver *drv = pci_dev_driver(pdev);
> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
> index e4b27aecbf05..79a2b5dfd694 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -598,6 +598,8 @@ static int pcistub_seize(struct pci_dev *dev,
>  	return err;
>  }
>  
> +static struct pci_driver xen_pcibk_pci_driver;
> +
>  /* Called when 'bind'. This means we must _NOT_ call pci_reset_function or
>   * other functions that take the sysfs lock. */
>  static int pcistub_probe(struct pci_dev *dev, const struct pci_device_id *id)
> @@ -609,8 +611,8 @@ static int pcistub_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  
>  	match = pcistub_match(dev);
>  
> -	if ((dev->driver_override &&
> -	     !strcmp(dev->driver_override, PCISTUB_DRIVER_NAME)) ||
> +	if (device_match_driver_override(&dev->dev,
> +					 &xen_pcibk_pci_driver.driver) > 0 ||
>  	    match) {
>  
>  		if (dev->hdr_type != PCI_HEADER_TYPE_NORMAL
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 1c270f1d5123..57e9463e4347 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -575,12 +575,6 @@ struct pci_dev {
>  	u8		supported_speeds; /* Supported Link Speeds Vector */
>  	phys_addr_t	rom;		/* Physical address if not from BAR */
>  	size_t		romlen;		/* Length if not from BAR */
> -	/*
> -	 * Driver name to force a match.  Do not set directly, because core
> -	 * frees it.  Use driver_set_override() to set or clear it.
> -	 */
> -	const char	*driver_override;
> -
>  	unsigned long	priv_flags;	/* Private flags for the PCI driver */
>  
>  	/* These methods index pci_reset_fn_methods[] */
> -- 
> 2.53.0
>