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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Will Deacon <will@kernel.org>
Cc: linux-kernel@vger.kernel.org, iommu@lists.linuxfoundation.org,
	kernel-team@android.com,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Jordan Crouse <jcrouse@codeaurora.org>,
	John Garry <john.garry@huawei.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Saravana Kannan <saravanak@google.com>,
	"Isaac J. Manjarres" <isaacm@codeaurora.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Joerg Roedel <joro@8bytes.org>, Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH v4 05/16] drivers/iommu: Take a ref to the IOMMU driver prior to ->add_device()
Date: Thu, 19 Dec 2019 15:44:37 +0100	[thread overview]
Message-ID: <20191219144437.GA1959534@kroah.com> (raw)
In-Reply-To: <20191219120352.382-6-will@kernel.org>

On Thu, Dec 19, 2019 at 12:03:41PM +0000, Will Deacon wrote:
> To avoid accidental removal of an active IOMMU driver module, take a
> reference to the driver module in 'iommu_probe_device()' immediately
> prior to invoking the '->add_device()' callback and hold it until the
> after the device has been removed by '->remove_device()'.
> 
> Suggested-by: Joerg Roedel <joro@8bytes.org>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  drivers/iommu/iommu.c | 19 +++++++++++++++++--
>  include/linux/iommu.h |  4 +++-
>  2 files changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 7c92197d53f3..bc8edf90e729 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -22,6 +22,7 @@
>  #include <linux/bitops.h>
>  #include <linux/property.h>
>  #include <linux/fsl/mc.h>
> +#include <linux/module.h>
>  #include <trace/events/iommu.h>
>  
>  static struct kset *iommu_group_kset;
> @@ -185,10 +186,21 @@ int iommu_probe_device(struct device *dev)
>  	if (!iommu_get_dev_param(dev))
>  		return -ENOMEM;
>  
> +	if (!try_module_get(ops->owner)) {
> +		ret = -EINVAL;
> +		goto err_free_dev_param;
> +	}
> +
>  	ret = ops->add_device(dev);
>  	if (ret)
> -		iommu_free_dev_param(dev);
> +		goto err_module_put;
> +
> +	return 0;
>  
> +err_module_put:
> +	module_put(ops->owner);
> +err_free_dev_param:
> +	iommu_free_dev_param(dev);
>  	return ret;
>  }
>  
> @@ -199,7 +211,10 @@ void iommu_release_device(struct device *dev)
>  	if (dev->iommu_group)
>  		ops->remove_device(dev);
>  
> -	iommu_free_dev_param(dev);
> +	if (dev->iommu_param) {
> +		module_put(ops->owner);
> +		iommu_free_dev_param(dev);
> +	}
>  }
>  
>  static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index f2223cbb5fd5..e9f94d3f7a04 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -246,9 +246,10 @@ struct iommu_iotlb_gather {
>   * @sva_get_pasid: Get PASID associated to a SVA handle
>   * @page_response: handle page request response
>   * @cache_invalidate: invalidate translation caches
> - * @pgsize_bitmap: bitmap of all possible supported page sizes
>   * @sva_bind_gpasid: bind guest pasid and mm
>   * @sva_unbind_gpasid: unbind guest pasid and mm
> + * @pgsize_bitmap: bitmap of all possible supported page sizes
> + * @owner: Driver module providing these ops
>   */
>  struct iommu_ops {
>  	bool (*capable)(enum iommu_cap);
> @@ -318,6 +319,7 @@ struct iommu_ops {
>  	int (*sva_unbind_gpasid)(struct device *dev, int pasid);
>  
>  	unsigned long pgsize_bitmap;
> +	struct module *owner;

Everyone is always going to forget to set this field.  I don't think you
even set it for all of the different iommu_ops possible in this series,
right?

The "trick" we did to keep people from having to remember this is to do
what we did for the bus registering functions.

Look at pci_register_driver in pci.h:
#define pci_register_driver(driver)             \
        __pci_register_driver(driver, THIS_MODULE, KBUILD_MODNAME)

Then we set the .owner field in the "real" __pci_register_driver() call.

Same thing for USB and lots, if not all, other driver register
functions.

You can do the same thing here, and I would recommend it.

No need to stop this series from happening now, just an add-on that is
easy to make to ensure that no one ever forgets to set this field
properly.

thanks,

greg k-h

WARNING: multiple messages have this Message-ID (diff)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Will Deacon <will@kernel.org>
Cc: iommu@lists.linuxfoundation.org,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Saravana Kannan <saravanak@google.com>,
	Robin Murphy <robin.murphy@arm.com>,
	linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	kernel-team@android.com,
	"Isaac J. Manjarres" <isaacm@codeaurora.org>
Subject: Re: [PATCH v4 05/16] drivers/iommu: Take a ref to the IOMMU driver prior to ->add_device()
Date: Thu, 19 Dec 2019 15:44:37 +0100	[thread overview]
Message-ID: <20191219144437.GA1959534@kroah.com> (raw)
In-Reply-To: <20191219120352.382-6-will@kernel.org>

On Thu, Dec 19, 2019 at 12:03:41PM +0000, Will Deacon wrote:
> To avoid accidental removal of an active IOMMU driver module, take a
> reference to the driver module in 'iommu_probe_device()' immediately
> prior to invoking the '->add_device()' callback and hold it until the
> after the device has been removed by '->remove_device()'.
> 
> Suggested-by: Joerg Roedel <joro@8bytes.org>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  drivers/iommu/iommu.c | 19 +++++++++++++++++--
>  include/linux/iommu.h |  4 +++-
>  2 files changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 7c92197d53f3..bc8edf90e729 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -22,6 +22,7 @@
>  #include <linux/bitops.h>
>  #include <linux/property.h>
>  #include <linux/fsl/mc.h>
> +#include <linux/module.h>
>  #include <trace/events/iommu.h>
>  
>  static struct kset *iommu_group_kset;
> @@ -185,10 +186,21 @@ int iommu_probe_device(struct device *dev)
>  	if (!iommu_get_dev_param(dev))
>  		return -ENOMEM;
>  
> +	if (!try_module_get(ops->owner)) {
> +		ret = -EINVAL;
> +		goto err_free_dev_param;
> +	}
> +
>  	ret = ops->add_device(dev);
>  	if (ret)
> -		iommu_free_dev_param(dev);
> +		goto err_module_put;
> +
> +	return 0;
>  
> +err_module_put:
> +	module_put(ops->owner);
> +err_free_dev_param:
> +	iommu_free_dev_param(dev);
>  	return ret;
>  }
>  
> @@ -199,7 +211,10 @@ void iommu_release_device(struct device *dev)
>  	if (dev->iommu_group)
>  		ops->remove_device(dev);
>  
> -	iommu_free_dev_param(dev);
> +	if (dev->iommu_param) {
> +		module_put(ops->owner);
> +		iommu_free_dev_param(dev);
> +	}
>  }
>  
>  static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index f2223cbb5fd5..e9f94d3f7a04 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -246,9 +246,10 @@ struct iommu_iotlb_gather {
>   * @sva_get_pasid: Get PASID associated to a SVA handle
>   * @page_response: handle page request response
>   * @cache_invalidate: invalidate translation caches
> - * @pgsize_bitmap: bitmap of all possible supported page sizes
>   * @sva_bind_gpasid: bind guest pasid and mm
>   * @sva_unbind_gpasid: unbind guest pasid and mm
> + * @pgsize_bitmap: bitmap of all possible supported page sizes
> + * @owner: Driver module providing these ops
>   */
>  struct iommu_ops {
>  	bool (*capable)(enum iommu_cap);
> @@ -318,6 +319,7 @@ struct iommu_ops {
>  	int (*sva_unbind_gpasid)(struct device *dev, int pasid);
>  
>  	unsigned long pgsize_bitmap;
> +	struct module *owner;

Everyone is always going to forget to set this field.  I don't think you
even set it for all of the different iommu_ops possible in this series,
right?

The "trick" we did to keep people from having to remember this is to do
what we did for the bus registering functions.

Look at pci_register_driver in pci.h:
#define pci_register_driver(driver)             \
        __pci_register_driver(driver, THIS_MODULE, KBUILD_MODNAME)

Then we set the .owner field in the "real" __pci_register_driver() call.

Same thing for USB and lots, if not all, other driver register
functions.

You can do the same thing here, and I would recommend it.

No need to stop this series from happening now, just an add-on that is
easy to make to ensure that no one ever forgets to set this field
properly.

thanks,

greg k-h
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2019-12-19 14:44 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-19 12:03 [PATCH v4 00/16] iommu: Permit modular builds of ARM SMMU[v3] drivers Will Deacon
2019-12-19 12:03 ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 01/16] drivers/iommu: Export core IOMMU API symbols to permit modular drivers Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 02/16] iommu/of: Request ACS from the PCI core when configuring IOMMU linkage Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 03/16] PCI/ATS: Restore EXPORT_SYMBOL_GPL() for pci_{enable,disable}_ats() Will Deacon
2019-12-19 12:03   ` [PATCH v4 03/16] PCI/ATS: Restore EXPORT_SYMBOL_GPL() for pci_{enable, disable}_ats() Will Deacon
2019-12-20  8:43   ` [PATCH v4 03/16] PCI/ATS: Restore EXPORT_SYMBOL_GPL() for pci_{enable,disable}_ats() Joerg Roedel
2019-12-20  8:43     ` Joerg Roedel
2019-12-20 15:03     ` Bjorn Helgaas
2019-12-20 15:03       ` Bjorn Helgaas
2019-12-19 12:03 ` [PATCH v4 04/16] PCI: Export pci_ats_disabled() as a GPL symbol to modules Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 05/16] drivers/iommu: Take a ref to the IOMMU driver prior to ->add_device() Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 14:44   ` Greg Kroah-Hartman [this message]
2019-12-19 14:44     ` Greg Kroah-Hartman
2020-01-09 14:16     ` Will Deacon
2020-01-09 14:16       ` Will Deacon
2020-01-09 18:17       ` Greg Kroah-Hartman
2020-01-09 18:17         ` Greg Kroah-Hartman
2019-12-19 12:03 ` [PATCH v4 06/16] iommu/of: Take a ref to the IOMMU driver during ->of_xlate() Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 07/16] drivers/iommu: Allow IOMMU bus ops to be unregistered Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 08/16] Revert "iommu/arm-smmu: Make arm-smmu-v3 explicitly non-modular" Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 09/16] Revert "iommu/arm-smmu: Make arm-smmu " Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 10/16] iommu/arm-smmu: Prevent forced unbinding of Arm SMMU drivers Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 11/16] iommu/arm-smmu-v3: Unregister IOMMU and bus ops on device removal Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 12/16] iommu/arm-smmu: Support SMMU module probing from the IORT Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 13/16] iommu/arm-smmu-v3: Allow building as a module Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 14/16] iommu/arm-smmu: Unregister IOMMU and bus ops on device removal Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 15/16] iommu/arm-smmu: Allow building as a module Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:03 ` [PATCH v4 16/16] iommu/arm-smmu: Update my email address in MODULE_AUTHOR() Will Deacon
2019-12-19 12:03   ` Will Deacon
2019-12-19 12:12 ` [PATCH v4 00/16] iommu: Permit modular builds of ARM SMMU[v3] drivers John Garry
2019-12-19 12:12   ` John Garry
2019-12-19 14:44 ` Greg Kroah-Hartman
2019-12-19 14:44   ` Greg Kroah-Hartman
2019-12-20 16:13 ` Joerg Roedel
2019-12-20 16:13   ` Joerg Roedel
2020-01-06 10:48   ` Will Deacon
2020-01-06 10:48     ` Will Deacon

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