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[PATCH v3 0/9] vfio: Fix release ordering races and use driver_override

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  [PATCH v3 0/9] vfio: Fix release ordering races and use  driver_override Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
    [PATCH v3 9/9] vfio: Add AMBA driver_override support Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
      Re: [PATCH v3 9/9] vfio: Add AMBA driver_override support Auger Eric <eric.auger@redhat.com> - 2017-06-26 09:40 +0200
    [PATCH v3 4/9] iommu: Add driver-not-bound notification Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
    [PATCH v3 6/9] vfio: Register pci, platform, amba,  and mdev bus drivers Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
    [PATCH v3 3/9] vfio: New external user group/file match Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
    [PATCH v3 1/9] vfio: Fix group release deadlock Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
    [PATCH v3 7/9] vfio: Use driver_override to avert binding to  compromising drivers Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
      Re: [PATCH v3 7/9] vfio: Use driver_override to avert binding to  compromising drivers Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-06-26 11:10 +0200
        Re: [PATCH v3 7/9] vfio: Use driver_override to avert binding to  compromising drivers Alex Williamson <alex.williamson@redhat.com> - 2017-06-26 21:40 +0200
    [PATCH v3 5/9] vfio: Create interface for vfio bus drivers to  register Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
    [PATCH v3 8/9] amba: Export amba_bustype Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:50 +0200
      Re: [PATCH v3 8/9] amba: Export amba_bustype Auger Eric <eric.auger@redhat.com> - 2017-06-26 09:40 +0200
    [PATCH v3 2/9] kvm-vfio: Decouple only when we match a group Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 18:00 +0200
      Re: [PATCH v3 2/9] kvm-vfio: Decouple only when we match a group Auger Eric <eric.auger@redhat.com> - 2017-06-26 09:40 +0200
      Re: [PATCH v3 2/9] kvm-vfio: Decouple only when we match a group Paolo Bonzini <pbonzini@redhat.com> - 2017-06-28 20:00 +0200
    Re: [PATCH v3 0/9] vfio: Fix release ordering races and use  driver_override Auger Eric <eric.auger@redhat.com> - 2017-06-26 09:40 +0200

#1670883 — [PATCH v3 0/9] vfio: Fix release ordering races and use driver_override

v3:

 * Fix Alexey's nit in 2/, which becomes a bug in 3/.  I posted the
   intended correction for this, but 0-day builds broke on it and I'd
   like to be sure we get all the automated testing possible, so v3.
   Added Alexey's Rb.

Thanks,

Alex

v2:

 * Added received acks and reviews, thanks!
 * Rebased and resolved conflict in patch 2/, dropped reviews due
   to changes and added Alexey to cc as spapr code is moved too
 * Added stable tag for patches 1-3
 * Resolved comment typo Eric noted in patch 1
 * Split AMBA out to patches 8 & 9 as Eric noted amba_bustype is
   not exported.  These can be separate follow-up patches if delayed

Please re-ack/review patch 2.  Eric, I'm happy to add your Tested-by
to the whole series if appropriate as well.  Thanks,

Alex


v1:

VM hotplug testing reveals a number of races in the vfio device,
group, container shutdown path, some attributed to libvirt's ask/take
unplug behavior and some long standing with groups potentially
composed of multiple devices, where each device can be independently
bound to drivers.  Libvirt's ask/take behavior is a result of the
asynchronous nature of PCI hotplug, libvirt registers a hot-unplug
request (ask), which is acknowledged almost immediately and then
proceeds to try to unbind the device from the vfio bus driver (take).
This sets us off on racing paths where we allow the device to be
released from the group much like would happen in groups with multiple
devices, while the group and container are torn down separately.
These races are addressed in the first 3 patches of this series.

The long standing issue with removing devices from in-use groups is
that we feel that the system is compromised if we allow user and host
devices within the same non-isolated group.  This triggers a BUG_ON
when we detect this condition after the rogue driver binding.  Since
that code was put in place we've added driver_override support for
all of the physical buses supported by vfio, giving us a way to block
binding to such compromising drivers.  We finally enable that in the
latter 4 patches of this series, minding that we need to allow
re-binding to non-compromising drivers, and also noting that a small
synchronization stall is effective in eliminating the need for this
blocking in the more common singleton device group case.

Reviews, comments, and acks appreciated.  Thanks,

Alex

---

Alex Williamson (9):
      vfio: Fix group release deadlock
      kvm-vfio: Decouple only when we match a group
      vfio: New external user group/file match
      iommu: Add driver-not-bound notification
      vfio: Create interface for vfio bus drivers to register
      vfio: Register pci, platform, amba, and mdev bus drivers
      vfio: Use driver_override to avert binding to compromising drivers
      amba: Export amba_bustype
      vfio: Add AMBA driver_override support


 drivers/amba/bus.c                    |    1 
 drivers/iommu/iommu.c                 |    3 
 drivers/vfio/mdev/vfio_mdev.c         |   13 ++
 drivers/vfio/pci/vfio_pci.c           |    7 +
 drivers/vfio/platform/vfio_amba.c     |   24 +++
 drivers/vfio/platform/vfio_platform.c |   24 +++
 drivers/vfio/vfio.c                   |  252 ++++++++++++++++++++++++++++++++-
 include/linux/iommu.h                 |    1 
 include/linux/vfio.h                  |    5 +
 virt/kvm/vfio.c                       |   40 +++--
 10 files changed, 344 insertions(+), 26 deletions(-)

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#1670886 — [PATCH v3 9/9] vfio: Add AMBA driver_override support

AMBA also supports driver_override, but amba_bustype was not exported
to be able to identify an amba device.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/vfio.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 20e57fecf652..36f0fcfded0b 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -36,6 +36,7 @@
 #include <linux/uuid.h>
 #include <linux/vfio.h>
 #include <linux/wait.h>
+#include <linux/amba/bus.h>
 
 #define DRIVER_VERSION	"0.3"
 #define DRIVER_AUTHOR	"Alex Williamson <alex.williamson@redhat.com>"
@@ -743,6 +744,11 @@ static char **vfio_find_driver_override(struct device *dev)
 	} else if (dev->bus == &platform_bus_type) {
 		struct platform_device *pdev = to_platform_device(dev);
 		return &pdev->driver_override;
+#ifdef CONFIG_ARM_AMBA
+	} else if (dev->bus == &amba_bustype) {
+		struct amba_device *adev = to_amba_device(dev);
+		return &adev->driver_override;
+#endif
 	}
 
 	return NULL;

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#1674507 — Re: [PATCH v3 9/9] vfio: Add AMBA driver_override support

Hi Alex,

On 20/06/2017 17:48, Alex Williamson wrote:
> AMBA also supports driver_override, but amba_bustype was not exported
> to be able to identify an amba device.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  drivers/vfio/vfio.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 20e57fecf652..36f0fcfded0b 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -36,6 +36,7 @@
>  #include <linux/uuid.h>
>  #include <linux/vfio.h>
>  #include <linux/wait.h>
> +#include <linux/amba/bus.h>
>  
>  #define DRIVER_VERSION	"0.3"
>  #define DRIVER_AUTHOR	"Alex Williamson <alex.williamson@redhat.com>"
> @@ -743,6 +744,11 @@ static char **vfio_find_driver_override(struct device *dev)
>  	} else if (dev->bus == &platform_bus_type) {
>  		struct platform_device *pdev = to_platform_device(dev);
>  		return &pdev->driver_override;
> +#ifdef CONFIG_ARM_AMBA
> +	} else if (dev->bus == &amba_bustype) {
> +		struct amba_device *adev = to_amba_device(dev);
> +		return &adev->driver_override;
> +#endif
>  	}
>  
>  	return NULL;
> 

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#1670887 — [PATCH v3 4/9] iommu: Add driver-not-bound notification

The driver core supports a BUS_NOTIFY_DRIVER_NOT_BOUND notification
sent if a driver fails to bind to a device.  Extend IOMMU group
notifications to include a version of this.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
---
 drivers/iommu/iommu.c |    3 +++
 include/linux/iommu.h |    1 +
 2 files changed, 4 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index cf7ca7e70777..1a59b3626ab2 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1139,6 +1139,9 @@ static int iommu_bus_notifier(struct notifier_block *nb,
 	case BUS_NOTIFY_UNBOUND_DRIVER:
 		group_action = IOMMU_GROUP_NOTIFY_UNBOUND_DRIVER;
 		break;
+	case BUS_NOTIFY_DRIVER_NOT_BOUND:
+		group_action = IOMMU_GROUP_NOTIFY_DRIVER_NOT_BOUND;
+		break;
 	}
 
 	if (group_action)
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 2cb54adc4a33..5f6b01398bc1 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -271,6 +271,7 @@ static inline void iommu_device_set_fwnode(struct iommu_device *iommu,
 #define IOMMU_GROUP_NOTIFY_BOUND_DRIVER		4 /* Post Driver bind */
 #define IOMMU_GROUP_NOTIFY_UNBIND_DRIVER	5 /* Pre Driver unbind */
 #define IOMMU_GROUP_NOTIFY_UNBOUND_DRIVER	6 /* Post Driver unbind */
+#define IOMMU_GROUP_NOTIFY_DRIVER_NOT_BOUND	7 /* Driver bind failed */
 
 extern int bus_set_iommu(struct bus_type *bus, const struct iommu_ops *ops);
 extern bool iommu_present(struct bus_type *bus);

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#1670891 — [PATCH v3 6/9] vfio: Register pci, platform, amba, and mdev bus drivers

Hook into vfio bus driver register/unregister support.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Cc: Baptiste Reynal <b.reynal@virtualopensystems.com>
Cc: Kirti Wankhede <kwankhede@nvidia.com>
---
 drivers/vfio/mdev/vfio_mdev.c         |   13 ++++++++++++-
 drivers/vfio/pci/vfio_pci.c           |    7 +++++++
 drivers/vfio/platform/vfio_amba.c     |   24 +++++++++++++++++++++++-
 drivers/vfio/platform/vfio_platform.c |   24 +++++++++++++++++++++++-
 4 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
index fa848a701b8b..b73d6f3e8ad5 100644
--- a/drivers/vfio/mdev/vfio_mdev.c
+++ b/drivers/vfio/mdev/vfio_mdev.c
@@ -131,11 +131,22 @@ struct mdev_driver vfio_mdev_driver = {
 
 static int __init vfio_mdev_init(void)
 {
-	return mdev_register_driver(&vfio_mdev_driver, THIS_MODULE);
+	int ret;
+
+	ret = mdev_register_driver(&vfio_mdev_driver, THIS_MODULE);
+	if (ret)
+		return ret;
+
+	ret = vfio_register_bus_driver(&vfio_mdev_driver.driver);
+	if (ret)
+		mdev_unregister_driver(&vfio_mdev_driver);
+
+	return ret;
 }
 
 static void __exit vfio_mdev_exit(void)
 {
+	vfio_unregister_bus_driver(&vfio_mdev_driver.driver);
 	mdev_unregister_driver(&vfio_mdev_driver);
 }
 
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 063c1ce6fa42..b9ac5b8c53e6 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1397,6 +1397,7 @@ static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev)
 
 static void __exit vfio_pci_cleanup(void)
 {
+	vfio_unregister_bus_driver(&vfio_pci_driver.driver);
 	pci_unregister_driver(&vfio_pci_driver);
 	vfio_pci_uninit_perm_bits();
 }
@@ -1456,6 +1457,12 @@ static int __init vfio_pci_init(void)
 	if (ret)
 		goto out_driver;
 
+	ret = vfio_register_bus_driver(&vfio_pci_driver.driver);
+	if (ret) {
+		pci_unregister_driver(&vfio_pci_driver);
+		goto out_driver;
+	}
+
 	vfio_pci_fill_ids();
 
 	return 0;
diff --git a/drivers/vfio/platform/vfio_amba.c b/drivers/vfio/platform/vfio_amba.c
index 31372fbf6c5b..7fd9cb4a6756 100644
--- a/drivers/vfio/platform/vfio_amba.c
+++ b/drivers/vfio/platform/vfio_amba.c
@@ -109,7 +109,29 @@ static int vfio_amba_remove(struct amba_device *adev)
 	},
 };
 
-module_amba_driver(vfio_amba_driver);
+static void __exit vfio_amba_exit(void)
+{
+	vfio_unregister_bus_driver(&vfio_amba_driver.drv);
+	amba_driver_unregister(&vfio_amba_driver);
+}
+
+static int __init vfio_amba_init(void)
+{
+	int ret;
+
+	ret = amba_driver_register(&vfio_amba_driver);
+	if (ret)
+		return ret;
+
+	ret = vfio_register_bus_driver(&vfio_amba_driver.drv);
+	if (ret)
+		amba_driver_unregister(&vfio_amba_driver);
+
+	return ret;
+}
+
+module_init(vfio_amba_init);
+module_exit(vfio_amba_exit);
 
 MODULE_VERSION(DRIVER_VERSION);
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c
index 6561751a1063..3974dc65e6dc 100644
--- a/drivers/vfio/platform/vfio_platform.c
+++ b/drivers/vfio/platform/vfio_platform.c
@@ -100,7 +100,29 @@ static int vfio_platform_remove(struct platform_device *pdev)
 	},
 };
 
-module_platform_driver(vfio_platform_driver);
+static void __exit vfio_platform_exit(void)
+{
+	vfio_unregister_bus_driver(&vfio_platform_driver.driver);
+	platform_driver_unregister(&vfio_platform_driver);
+}
+
+static int __init vfio_platform_init(void)
+{
+	int ret;
+
+	ret = platform_driver_register(&vfio_platform_driver);
+	if (ret)
+		return ret;
+
+	ret = vfio_register_bus_driver(&vfio_platform_driver.driver);
+	if (ret)
+		platform_driver_unregister(&vfio_platform_driver);
+
+	return ret;
+}
+
+module_init(vfio_platform_init);
+module_exit(vfio_platform_exit);
 
 MODULE_VERSION(DRIVER_VERSION);
 MODULE_LICENSE("GPL v2");

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#1670892 — [PATCH v3 3/9] vfio: New external user group/file match

At the point where the kvm-vfio pseudo device wants to release its
vfio group reference, we can't always acquire a new reference to make
that happen.  The group can be in a state where we wouldn't allow a
new reference to be added.  This new helper function allows a caller
to match a file to a group to facilitate this.  Given a file and
group, report if they match.  Thus the caller needs to already have a
group reference to match to the file.  This allows the deletion of a
group without acquiring a new reference.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
---
 drivers/vfio/vfio.c  |    9 +++++++++
 include/linux/vfio.h |    2 ++
 virt/kvm/vfio.c      |   27 +++++++++++++++++++--------
 3 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 54dd2fbf83d9..7597a377eb4e 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1776,6 +1776,15 @@ void vfio_group_put_external_user(struct vfio_group *group)
 }
 EXPORT_SYMBOL_GPL(vfio_group_put_external_user);
 
+bool vfio_external_group_match_file(struct vfio_group *test_group,
+				    struct file *filep)
+{
+	struct vfio_group *group = filep->private_data;
+
+	return (filep->f_op == &vfio_group_fops) && (group == test_group);
+}
+EXPORT_SYMBOL_GPL(vfio_external_group_match_file);
+
 int vfio_external_user_iommu_id(struct vfio_group *group)
 {
 	return iommu_group_id(group->iommu_group);
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index edf9b2cad277..9b34d0af5d27 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -97,6 +97,8 @@ extern void vfio_unregister_iommu_driver(
  */
 extern struct vfio_group *vfio_group_get_external_user(struct file *filep);
 extern void vfio_group_put_external_user(struct vfio_group *group);
+extern bool vfio_external_group_match_file(struct vfio_group *group,
+					   struct file *filep);
 extern int vfio_external_user_iommu_id(struct vfio_group *group);
 extern long vfio_external_check_extension(struct vfio_group *group,
 					  unsigned long arg);
diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
index 6e002d0f3191..d99850c462a1 100644
--- a/virt/kvm/vfio.c
+++ b/virt/kvm/vfio.c
@@ -51,6 +51,22 @@ static struct vfio_group *kvm_vfio_group_get_external_user(struct file *filep)
 	return vfio_group;
 }
 
+static bool kvm_vfio_external_group_match_file(struct vfio_group *group,
+					       struct file *filep)
+{
+	bool ret, (*fn)(struct vfio_group *, struct file *);
+
+	fn = symbol_get(vfio_external_group_match_file);
+	if (!fn)
+		return false;
+
+	ret = fn(group, filep);
+
+	symbol_put(vfio_external_group_match_file);
+
+	return ret;
+}
+
 static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
 {
 	void (*fn)(struct vfio_group *);
@@ -231,18 +247,13 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
 		if (!f.file)
 			return -EBADF;
 
-		vfio_group = kvm_vfio_group_get_external_user(f.file);
-		fdput(f);
-
-		if (IS_ERR(vfio_group))
-			return PTR_ERR(vfio_group);
-
 		ret = -ENOENT;
 
 		mutex_lock(&kv->lock);
 
 		list_for_each_entry(kvg, &kv->group_list, node) {
-			if (kvg->vfio_group != vfio_group)
+			if (!kvm_vfio_external_group_match_file(kvg->vfio_group,
+								f.file))
 				continue;
 
 			list_del(&kvg->node);
@@ -260,7 +271,7 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
 
 		mutex_unlock(&kv->lock);
 
-		kvm_vfio_group_put_external_user(vfio_group);
+		fdput(f);
 
 		kvm_vfio_update_coherency(dev);
 

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#1670893 — [PATCH v3 1/9] vfio: Fix group release deadlock

If vfio_iommu_group_notifier() acquires a group reference and that
reference becomes the last reference to the group, then vfio_group_put
introduces a deadlock code path where we're trying to unregister from
the iommu notifier chain from within a callout of that chain.  Use a
work_struct to release this reference asynchronously.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Cc: stable@vger.kernel.org
---
 drivers/vfio/vfio.c |   37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 6a49485eb49d..54dd2fbf83d9 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -423,6 +423,34 @@ static void vfio_group_put(struct vfio_group *group)
 	kref_put_mutex(&group->kref, vfio_group_release, &vfio.group_lock);
 }
 
+struct vfio_group_put_work {
+	struct work_struct work;
+	struct vfio_group *group;
+};
+
+static void vfio_group_put_bg(struct work_struct *work)
+{
+	struct vfio_group_put_work *do_work;
+
+	do_work = container_of(work, struct vfio_group_put_work, work);
+
+	vfio_group_put(do_work->group);
+	kfree(do_work);
+}
+
+static void vfio_group_schedule_put(struct vfio_group *group)
+{
+	struct vfio_group_put_work *do_work;
+
+	do_work = kmalloc(sizeof(*do_work), GFP_KERNEL);
+	if (WARN_ON(!do_work))
+		return;
+
+	INIT_WORK(&do_work->work, vfio_group_put_bg);
+	do_work->group = group;
+	schedule_work(&do_work->work);
+}
+
 /* Assume group_lock or group reference is held */
 static void vfio_group_get(struct vfio_group *group)
 {
@@ -762,7 +790,14 @@ static int vfio_iommu_group_notifier(struct notifier_block *nb,
 		break;
 	}
 
-	vfio_group_put(group);
+	/*
+	 * If we're the last reference to the group, the group will be
+	 * released, which includes unregistering the iommu group notifier.
+	 * We hold a read-lock on that notifier list, unregistering needs
+	 * a write-lock... deadlock.  Release our reference asynchronously
+	 * to avoid that situation.
+	 */
+	vfio_group_schedule_put(group);
 	return NOTIFY_OK;
 }
 

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#1670896 — [PATCH v3 7/9] vfio: Use driver_override to avert binding to compromising drivers

If a device is bound to a non-vfio, non-whitelisted driver while a
group is in use, then the integrity of the group is compromised and
will result in hitting a BUG_ON.  This code tries to avoid this case
by mangling driver_override to force a no-match for the driver.  The
driver-core will either follow-up with a DRIVER_NOT_BOUND (preferred)
or BOUND_DRIVER, at which point we can remove the driver_override
mangling.

A complication here is that even though the window between these
notifications is expected to be extremely small, the vfio group could
be removed, which would prevent us from finding the group again to
remove the driver_override.  We therefore take a group reference when
adding to driver_override and release it when removed.  A second
complication is that driver_override can be modified by the system
admin through sysfs.  To avoid trivial interference, we add a non-
user-visible UUID to the group and use this as part of the mangle
string.

The above blocks binding to a driver that would compromise the host,
but we'd also like to avoid reaching that step if possible.  For this
we add a wait_event_timeout() with a short, 1 second timeout, which is
highly effective in allowing empty groups to finish cleanup.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
---
 drivers/vfio/vfio.c |  145 +++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 138 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index f40d1508d368..20e57fecf652 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -25,6 +25,7 @@
 #include <linux/miscdevice.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/platform_device.h>
 #include <linux/pci.h>
 #include <linux/rwsem.h>
 #include <linux/sched.h>
@@ -32,6 +33,7 @@
 #include <linux/stat.h>
 #include <linux/string.h>
 #include <linux/uaccess.h>
+#include <linux/uuid.h>
 #include <linux/vfio.h>
 #include <linux/wait.h>
 
@@ -95,6 +97,7 @@ struct vfio_group {
 	bool				noiommu;
 	struct kvm			*kvm;
 	struct blocking_notifier_head	notifier;
+	unsigned char			uuid[16];
 };
 
 struct vfio_device {
@@ -352,6 +355,8 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)
 
 	group->nb.notifier_call = vfio_iommu_group_notifier;
 
+	generate_random_uuid(group->uuid);
+
 	/*
 	 * blocking notifiers acquire a rwsem around registering and hold
 	 * it around callback.  Therefore, need to register outside of
@@ -728,6 +733,111 @@ static int vfio_group_nb_verify(struct vfio_group *group, struct device *dev)
 	return vfio_dev_viable(dev, group);
 }
 
+#define VFIO_TAG_PREFIX "#vfio_group:"
+
+static char **vfio_find_driver_override(struct device *dev)
+{
+	if (dev_is_pci(dev)) {
+		struct pci_dev *pdev = to_pci_dev(dev);
+		return &pdev->driver_override;
+	} else if (dev->bus == &platform_bus_type) {
+		struct platform_device *pdev = to_platform_device(dev);
+		return &pdev->driver_override;
+	}
+
+	return NULL;
+}
+
+/*
+ * If we're about to bind to something other than a known whitelisted driver
+ * or known vfio bus driver, try to avert it with driver_override.
+ */
+static void vfio_group_nb_pre_bind(struct vfio_group *group, struct device *dev)
+{
+	struct vfio_bus_driver *driver;
+	struct device_driver *drv = ACCESS_ONCE(dev->driver);
+	char **driver_override;
+
+	if (vfio_dev_whitelisted(dev, drv))
+		return; /* Binding to known "innocuous" device/driver */
+
+	mutex_lock(&vfio.bus_drivers_lock);
+	list_for_each_entry(driver, &vfio.bus_drivers_list, vfio_next) {
+		if (driver->drv == drv) {
+			mutex_unlock(&vfio.bus_drivers_lock);
+			return; /* Binding to known vfio bus driver, ok */
+		}
+	}
+	mutex_unlock(&vfio.bus_drivers_lock);
+
+	/* Can we stall slightly to let users fall off? */
+	if (list_empty(&group->device_list)) {
+		if (wait_event_timeout(vfio.release_q,
+				!atomic_read(&group->container_users), HZ))
+			return;
+	}
+
+	driver_override = vfio_find_driver_override(dev);
+	if (driver_override) {
+		char tag[50], *new = NULL, *old = *driver_override;
+
+		snprintf(tag, sizeof(tag), "%s%pU",
+			 VFIO_TAG_PREFIX, group->uuid);
+
+		if (old && strstr(old, tag))
+			return; /* block already in place */
+
+		new = kasprintf(GFP_KERNEL, "%s%s", old ? old : "", tag);
+		if (new) {
+			*driver_override = new;
+			kfree(old);
+			vfio_group_get(group);
+			dev_warn(dev, "vfio: Blocking unsafe driver bind\n");
+			return;
+		}
+	}
+
+	dev_warn(dev, "vfio: Unsafe driver binding to in-use group!\n");
+}
+
+/* If we've mangled driver_override, remove it */
+static void vfio_group_nb_post_bind(struct vfio_group *group,
+				    struct device *dev)
+{
+	char **driver_override = vfio_find_driver_override(dev);
+
+	if (driver_override && *driver_override) {
+		char tag[50], *new, *start, *end, *old = *driver_override;
+
+		snprintf(tag, sizeof(tag), "%s%pU",
+			 VFIO_TAG_PREFIX, group->uuid);
+
+		start = strstr(old, tag);
+		if (start) {
+			end = start + strlen(tag);
+
+			if (old + strlen(old) > end)
+				memmove(start, end,
+					strlen(old) - (end - old) + 1);
+			else
+				*start = 0;
+
+			if (strlen(old)) {
+				new = kasprintf(GFP_KERNEL, "%s", old);
+				if (new) {
+					*driver_override = new;
+					kfree(old);
+				} /* else, in-place terminated, ok */
+			} else {
+				*driver_override = NULL;
+				kfree(old);
+			}
+
+			vfio_group_put(group);
+		}
+	}
+}
+
 static int vfio_iommu_group_notifier(struct notifier_block *nb,
 				     unsigned long action, void *data)
 {
@@ -757,14 +867,23 @@ static int vfio_iommu_group_notifier(struct notifier_block *nb,
 		 */
 		break;
 	case IOMMU_GROUP_NOTIFY_BIND_DRIVER:
-		pr_debug("%s: Device %s, group %d binding to driver\n",
+		pr_debug("%s: Device %s, group %d binding to driver %s\n",
 			 __func__, dev_name(dev),
-			 iommu_group_id(group->iommu_group));
+			 iommu_group_id(group->iommu_group), dev->driver->name);
+		if (vfio_group_nb_verify(group, dev))
+			vfio_group_nb_pre_bind(group, dev);
+		break;
+	case IOMMU_GROUP_NOTIFY_DRIVER_NOT_BOUND:
+		pr_debug("%s: Device %s, group %d binding fail to driver %s\n",
+			 __func__, dev_name(dev),
+			 iommu_group_id(group->iommu_group), dev->driver->name);
+		vfio_group_nb_post_bind(group, dev);
 		break;
 	case IOMMU_GROUP_NOTIFY_BOUND_DRIVER:
 		pr_debug("%s: Device %s, group %d bound to driver %s\n",
 			 __func__, dev_name(dev),
 			 iommu_group_id(group->iommu_group), dev->driver->name);
+		vfio_group_nb_post_bind(group, dev);
 		BUG_ON(vfio_group_nb_verify(group, dev));
 		break;
 	case IOMMU_GROUP_NOTIFY_UNBIND_DRIVER:
@@ -1351,6 +1470,7 @@ static int vfio_group_unset_container(struct vfio_group *group)
 	if (users != 1)
 		return -EBUSY;
 
+	wake_up(&vfio.release_q);
 	__vfio_group_unset_container(group);
 
 	return 0;
@@ -1364,7 +1484,11 @@ static int vfio_group_unset_container(struct vfio_group *group)
  */
 static void vfio_group_try_dissolve_container(struct vfio_group *group)
 {
-	if (0 == atomic_dec_if_positive(&group->container_users))
+	int users = atomic_dec_if_positive(&group->container_users);
+
+	wake_up(&vfio.release_q);
+
+	if (!users)
 		__vfio_group_unset_container(group);
 }
 
@@ -1433,19 +1557,26 @@ static bool vfio_group_viable(struct vfio_group *group)
 
 static int vfio_group_add_container_user(struct vfio_group *group)
 {
+	int ret;
+
 	if (!atomic_inc_not_zero(&group->container_users))
 		return -EINVAL;
 
 	if (group->noiommu) {
-		atomic_dec(&group->container_users);
-		return -EPERM;
+		ret = -EPERM;
+		goto out;
 	}
 	if (!group->container->iommu_driver || !vfio_group_viable(group)) {
-		atomic_dec(&group->container_users);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out;
 	}
 
 	return 0;
+
+out:
+	atomic_dec(&group->container_users);
+	wake_up(&vfio.release_q);
+	return ret;
 }
 
 static const struct file_operations vfio_device_fops;

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#1674543 — Re: [PATCH v3 7/9] vfio: Use driver_override to avert binding to compromising drivers

On Tue, Jun 20, 2017 at 09:48:31AM -0600, Alex Williamson wrote:
> If a device is bound to a non-vfio, non-whitelisted driver while a
> group is in use, then the integrity of the group is compromised and
> will result in hitting a BUG_ON.  This code tries to avoid this case
> by mangling driver_override to force a no-match for the driver.  The
> driver-core will either follow-up with a DRIVER_NOT_BOUND (preferred)
> or BOUND_DRIVER, at which point we can remove the driver_override
> mangling.

Rather than mangling the driver override string to prevent driver binding,
I wonder if it would make more sense to allow the BUS_NOTIFY_BIND_DRIVER
notifier to fail the device probe?

The driver override strings are, after all, exposed to userspace, and
it strikes me that this kind of mangling is racy - userspace can read
or change the override string at any time.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

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#1675062 — Re: [PATCH v3 7/9] vfio: Use driver_override to avert binding to compromising drivers

On Mon, 26 Jun 2017 10:08:55 +0100
Russell King - ARM Linux <linux@armlinux.org.uk> wrote:

> On Tue, Jun 20, 2017 at 09:48:31AM -0600, Alex Williamson wrote:
> > If a device is bound to a non-vfio, non-whitelisted driver while a
> > group is in use, then the integrity of the group is compromised and
> > will result in hitting a BUG_ON.  This code tries to avoid this case
> > by mangling driver_override to force a no-match for the driver.  The
> > driver-core will either follow-up with a DRIVER_NOT_BOUND (preferred)
> > or BOUND_DRIVER, at which point we can remove the driver_override
> > mangling.  
> 
> Rather than mangling the driver override string to prevent driver binding,
> I wonder if it would make more sense to allow the BUS_NOTIFY_BIND_DRIVER
> notifier to fail the device probe?
> 
> The driver override strings are, after all, exposed to userspace, and
> it strikes me that this kind of mangling is racy - userspace can read
> or change the override string at any time.

Indeed, that looks easier.  I sent and RFC, let's see what Greg has to
say.  Thanks,

Alex

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#1670898 — [PATCH v3 5/9] vfio: Create interface for vfio bus drivers to register

Generally we don't know about vfio bus drivers until a device is
added to the vfio-core with vfio_add_group_dev(), this optional
registration with vfio_register_bus_driver() allows vfio-core to
track known drivers.  Our current use for this information is to
know whether a driver is vfio compatible during a bind operation.
For devices on buses with driver_override support, we can use this
linkage to block non-vfio drivers from binding to devices where
the iommu group state would trigger a BUG to avoid host/user
integrity issues.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
---
 drivers/vfio/vfio.c  |   55 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/vfio.h |    3 +++
 2 files changed, 58 insertions(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 7597a377eb4e..f40d1508d368 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -43,6 +43,8 @@
 	struct class			*class;
 	struct list_head		iommu_drivers_list;
 	struct mutex			iommu_drivers_lock;
+	struct list_head		bus_drivers_list;
+	struct mutex			bus_drivers_lock;
 	struct list_head		group_list;
 	struct idr			group_idr;
 	struct mutex			group_lock;
@@ -51,6 +53,11 @@
 	wait_queue_head_t		release_q;
 } vfio;
 
+struct vfio_bus_driver {
+	struct device_driver		*drv;
+	struct list_head		vfio_next;
+};
+
 struct vfio_iommu_driver {
 	const struct vfio_iommu_driver_ops	*ops;
 	struct list_head			vfio_next;
@@ -2243,6 +2250,52 @@ int vfio_unregister_notifier(struct device *dev, enum vfio_notify_type type,
 }
 EXPORT_SYMBOL(vfio_unregister_notifier);
 
+int vfio_register_bus_driver(struct device_driver *drv)
+{
+	struct vfio_bus_driver *driver, *tmp;
+
+	driver = kzalloc(sizeof(*driver), GFP_KERNEL);
+	if (!driver)
+		return -ENOMEM;
+
+	driver->drv = drv;
+
+	mutex_lock(&vfio.bus_drivers_lock);
+
+	/* Check for duplicates */
+	list_for_each_entry(tmp, &vfio.bus_drivers_list, vfio_next) {
+		if (tmp->drv == drv) {
+			mutex_unlock(&vfio.bus_drivers_lock);
+			kfree(driver);
+			return -EINVAL;
+		}
+	}
+
+	list_add(&driver->vfio_next, &vfio.bus_drivers_list);
+
+	mutex_unlock(&vfio.bus_drivers_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vfio_register_bus_driver);
+
+void vfio_unregister_bus_driver(struct device_driver *drv)
+{
+	struct vfio_bus_driver *driver;
+
+	mutex_lock(&vfio.bus_drivers_lock);
+	list_for_each_entry(driver, &vfio.bus_drivers_list, vfio_next) {
+		if (driver->drv == drv) {
+			list_del(&driver->vfio_next);
+			mutex_unlock(&vfio.bus_drivers_lock);
+			kfree(driver);
+			return;
+		}
+	}
+	mutex_unlock(&vfio.bus_drivers_lock);
+}
+EXPORT_SYMBOL_GPL(vfio_unregister_bus_driver);
+
 /**
  * Module/class support
  */
@@ -2266,8 +2319,10 @@ static int __init vfio_init(void)
 	idr_init(&vfio.group_idr);
 	mutex_init(&vfio.group_lock);
 	mutex_init(&vfio.iommu_drivers_lock);
+	mutex_init(&vfio.bus_drivers_lock);
 	INIT_LIST_HEAD(&vfio.group_list);
 	INIT_LIST_HEAD(&vfio.iommu_drivers_list);
+	INIT_LIST_HEAD(&vfio.bus_drivers_list);
 	init_waitqueue_head(&vfio.release_q);
 
 	ret = misc_register(&vfio_dev);
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 9b34d0af5d27..dab0f8105e4a 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -92,6 +92,9 @@ struct vfio_iommu_driver_ops {
 extern void vfio_unregister_iommu_driver(
 				const struct vfio_iommu_driver_ops *ops);
 
+extern int vfio_register_bus_driver(struct device_driver *drv);
+extern void vfio_unregister_bus_driver(struct device_driver *drv);
+
 /*
  * External user API
  */

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#1670900 — [PATCH v3 8/9] amba: Export amba_bustype

This allows modules to match struct device.bus to amba_bustype for the
purpose of casting the device to an amba_device with to_amba_device().

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reported-by: Eric Auger <eric.auger@redhat.com>
Cc: Russell King <linux@armlinux.org.uk>
---
 drivers/amba/bus.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index a56fa2a1e9aa..4e118cd3ddf3 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -197,6 +197,7 @@ struct bus_type amba_bustype = {
 	.uevent		= amba_uevent,
 	.pm		= &amba_pm,
 };
+EXPORT_SYMBOL_GPL(amba_bustype);
 
 static int __init amba_init(void)
 {

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#1674496 — Re: [PATCH v3 8/9] amba: Export amba_bustype

Hi Alex,

On 20/06/2017 17:48, Alex Williamson wrote:
> This allows modules to match struct device.bus to amba_bustype for the
> purpose of casting the device to an amba_device with to_amba_device().
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Reported-by: Eric Auger <eric.auger@redhat.com>
> Cc: Russell King <linux@armlinux.org.uk>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
>  drivers/amba/bus.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
> index a56fa2a1e9aa..4e118cd3ddf3 100644
> --- a/drivers/amba/bus.c
> +++ b/drivers/amba/bus.c
> @@ -197,6 +197,7 @@ struct bus_type amba_bustype = {
>  	.uevent		= amba_uevent,
>  	.pm		= &amba_pm,
>  };
> +EXPORT_SYMBOL_GPL(amba_bustype);
>  
>  static int __init amba_init(void)
>  {
> 

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#1670903 — [PATCH v3 2/9] kvm-vfio: Decouple only when we match a group

Unset-KVM and decrement-assignment only when we find the group in our
list.  Otherwise we can get out of sync if the user triggers this for
groups that aren't currently on our list.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: stable@vger.kernel.org
---
 virt/kvm/vfio.c |   13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
index 37d9118fd84b..6e002d0f3191 100644
--- a/virt/kvm/vfio.c
+++ b/virt/kvm/vfio.c
@@ -246,21 +246,20 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
 				continue;
 
 			list_del(&kvg->node);
+			kvm_arch_end_assignment(dev->kvm);
+#ifdef CONFIG_SPAPR_TCE_IOMMU
+			kvm_spapr_tce_release_vfio_group(dev->kvm,
+							 kvg->vfio_group);
+#endif
+			kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
 			kvm_vfio_group_put_external_user(kvg->vfio_group);
 			kfree(kvg);
 			ret = 0;
 			break;
 		}
 
-		kvm_arch_end_assignment(dev->kvm);
-
 		mutex_unlock(&kv->lock);
 
-#ifdef CONFIG_SPAPR_TCE_IOMMU
-		kvm_spapr_tce_release_vfio_group(dev->kvm, vfio_group);
-#endif
-		kvm_vfio_group_set_kvm(vfio_group, NULL);
-
 		kvm_vfio_group_put_external_user(vfio_group);
 
 		kvm_vfio_update_coherency(dev);

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#1674495 — Re: [PATCH v3 2/9] kvm-vfio: Decouple only when we match a group

Hi,
On 20/06/2017 17:47, Alex Williamson wrote:
> Unset-KVM and decrement-assignment only when we find the group in our
> list.  Otherwise we can get out of sync if the user triggers this for
> groups that aren't currently on our list.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
>  virt/kvm/vfio.c |   13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index 37d9118fd84b..6e002d0f3191 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -246,21 +246,20 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
>  				continue;
>  
>  			list_del(&kvg->node);
> +			kvm_arch_end_assignment(dev->kvm);
> +#ifdef CONFIG_SPAPR_TCE_IOMMU
> +			kvm_spapr_tce_release_vfio_group(dev->kvm,
> +							 kvg->vfio_group);
> +#endif
> +			kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
>  			kvm_vfio_group_put_external_user(kvg->vfio_group);
>  			kfree(kvg);
>  			ret = 0;
>  			break;
>  		}
>  
> -		kvm_arch_end_assignment(dev->kvm);
> -
>  		mutex_unlock(&kv->lock);
>  
> -#ifdef CONFIG_SPAPR_TCE_IOMMU
> -		kvm_spapr_tce_release_vfio_group(dev->kvm, vfio_group);
> -#endif
> -		kvm_vfio_group_set_kvm(vfio_group, NULL);
> -
>  		kvm_vfio_group_put_external_user(vfio_group);
>  
>  		kvm_vfio_update_coherency(dev);
> 

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#1677007 — Re: [PATCH v3 2/9] kvm-vfio: Decouple only when we match a group

On 20/06/2017 17:47, Alex Williamson wrote:
> Unset-KVM and decrement-assignment only when we find the group in our
> list.  Otherwise we can get out of sync if the user triggers this for
> groups that aren't currently on our list.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: stable@vger.kernel.org
> ---
>  virt/kvm/vfio.c |   13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index 37d9118fd84b..6e002d0f3191 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -246,21 +246,20 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
>  				continue;
>  
>  			list_del(&kvg->node);
> +			kvm_arch_end_assignment(dev->kvm);
> +#ifdef CONFIG_SPAPR_TCE_IOMMU
> +			kvm_spapr_tce_release_vfio_group(dev->kvm,
> +							 kvg->vfio_group);
> +#endif
> +			kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
>  			kvm_vfio_group_put_external_user(kvg->vfio_group);
>  			kfree(kvg);
>  			ret = 0;
>  			break;
>  		}
>  
> -		kvm_arch_end_assignment(dev->kvm);
> -
>  		mutex_unlock(&kv->lock);
>  
> -#ifdef CONFIG_SPAPR_TCE_IOMMU
> -		kvm_spapr_tce_release_vfio_group(dev->kvm, vfio_group);
> -#endif
> -		kvm_vfio_group_set_kvm(vfio_group, NULL);
> -
>  		kvm_vfio_group_put_external_user(vfio_group);
>  
>  		kvm_vfio_update_coherency(dev);
> 
> 

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Thanks,

Paolo

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#1674498

Hi Alex,

On 20/06/2017 17:47, Alex Williamson wrote:
> v3:
> 
>  * Fix Alexey's nit in 2/, which becomes a bug in 3/.  I posted the
>    intended correction for this, but 0-day builds broke on it and I'd
>    like to be sure we get all the automated testing possible, so v3.
>    Added Alexey's Rb.

I tested non regression with vfio-platform.

"vfio: Use driver_override to avert binding to compromising drivers"
modality was tested with vfio-pci on aarch64 AMD Overdrive system (2 igb
PFs in the same group).

Feel free to add my Tested-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

> 
> Thanks,
> 
> Alex
> 
> v2:
> 
>  * Added received acks and reviews, thanks!
>  * Rebased and resolved conflict in patch 2/, dropped reviews due
>    to changes and added Alexey to cc as spapr code is moved too
>  * Added stable tag for patches 1-3
>  * Resolved comment typo Eric noted in patch 1
>  * Split AMBA out to patches 8 & 9 as Eric noted amba_bustype is
>    not exported.  These can be separate follow-up patches if delayed
> 
> Please re-ack/review patch 2.  Eric, I'm happy to add your Tested-by
> to the whole series if appropriate as well.  Thanks,
> 
> Alex
> 
> 
> v1:
> 
> VM hotplug testing reveals a number of races in the vfio device,
> group, container shutdown path, some attributed to libvirt's ask/take
> unplug behavior and some long standing with groups potentially
> composed of multiple devices, where each device can be independently
> bound to drivers.  Libvirt's ask/take behavior is a result of the
> asynchronous nature of PCI hotplug, libvirt registers a hot-unplug
> request (ask), which is acknowledged almost immediately and then
> proceeds to try to unbind the device from the vfio bus driver (take).
> This sets us off on racing paths where we allow the device to be
> released from the group much like would happen in groups with multiple
> devices, while the group and container are torn down separately.
> These races are addressed in the first 3 patches of this series.
> 
> The long standing issue with removing devices from in-use groups is
> that we feel that the system is compromised if we allow user and host
> devices within the same non-isolated group.  This triggers a BUG_ON
> when we detect this condition after the rogue driver binding.  Since
> that code was put in place we've added driver_override support for
> all of the physical buses supported by vfio, giving us a way to block
> binding to such compromising drivers.  We finally enable that in the
> latter 4 patches of this series, minding that we need to allow
> re-binding to non-compromising drivers, and also noting that a small
> synchronization stall is effective in eliminating the need for this
> blocking in the more common singleton device group case.
> 
> Reviews, comments, and acks appreciated.  Thanks,
> 
> Alex
> 
> ---
> 
> Alex Williamson (9):
>       vfio: Fix group release deadlock
>       kvm-vfio: Decouple only when we match a group
>       vfio: New external user group/file match
>       iommu: Add driver-not-bound notification
>       vfio: Create interface for vfio bus drivers to register
>       vfio: Register pci, platform, amba, and mdev bus drivers
>       vfio: Use driver_override to avert binding to compromising drivers
>       amba: Export amba_bustype
>       vfio: Add AMBA driver_override support
> 
> 
>  drivers/amba/bus.c                    |    1 
>  drivers/iommu/iommu.c                 |    3 
>  drivers/vfio/mdev/vfio_mdev.c         |   13 ++
>  drivers/vfio/pci/vfio_pci.c           |    7 +
>  drivers/vfio/platform/vfio_amba.c     |   24 +++
>  drivers/vfio/platform/vfio_platform.c |   24 +++
>  drivers/vfio/vfio.c                   |  252 ++++++++++++++++++++++++++++++++-
>  include/linux/iommu.h                 |    1 
>  include/linux/vfio.h                  |    5 +
>  virt/kvm/vfio.c                       |   40 +++--
>  10 files changed, 344 insertions(+), 26 deletions(-)
> 

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