[PATCH] iommu/core: fix bus notifier breakage

[PATCH] iommu/core: fix bus notifier breakage

[Mark Salter]

iommu_bus_init() registers a bus notifier on the given bus by using
a statically defined notifier block:

  static struct notifier_block iommu_bus_nb = {
          .notifier_call = iommu_bus_notifier,
  };

This same notifier block is used for all busses. This causes a
problem for notifiers registered after iommu has registered this
callback on multiple busses. The problem is that a subsequent
notifier being registered on a bus which has this iommu notifier
will also get linked in to the notifier list of all other busses
which have this iommu notifier.

This patch fixes this by allocating the notifier_block at runtime.
Some error checking is also added to catch any allocation failure
or notifier registration error.

Signed-off-by: Mark Salter <msalter@redhat.com>
---
 drivers/iommu/iommu.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 0639b92..f00697a 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -770,18 +770,26 @@ static int iommu_bus_notifier(struct notifier_block *nb,
 	return 0;
 }
 
-static struct notifier_block iommu_bus_nb = {
-	.notifier_call = iommu_bus_notifier,
-};
-
-static void iommu_bus_init(struct bus_type *bus, const struct iommu_ops *ops)
+static int iommu_bus_init(struct bus_type *bus, const struct iommu_ops *ops)
 {
+	int err;
+	struct notifier_block *nb;
 	struct iommu_callback_data cb = {
 		.ops = ops,
 	};
 
-	bus_register_notifier(bus, &iommu_bus_nb);
-	bus_for_each_dev(bus, NULL, &cb, add_iommu_group);
+	nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL);
+	if (!nb)
+		return -ENOMEM;
+
+	nb->notifier_call = iommu_bus_notifier;
+
+	err = bus_register_notifier(bus, nb);
+	if (err) {
+		kfree(nb);
+		return err;
+	}
+	return bus_for_each_dev(bus, NULL, &cb, add_iommu_group);
 }
 
 /**
@@ -805,9 +813,7 @@ int bus_set_iommu(struct bus_type *bus, const struct iommu_ops *ops)
 	bus->iommu_ops = ops;
 
 	/* Do IOMMU specific setup for this bus-type */
-	iommu_bus_init(bus, ops);
-
-	return 0;
+	return iommu_bus_init(bus, ops);
 }
 EXPORT_SYMBOL_GPL(bus_set_iommu);
 
-- 
1.9.3

Re: [PATCH] iommu/core: fix bus notifier breakage

[Joerg Roedel]

On Sun, Sep 21, 2014 at 01:58:24PM -0400, Mark Salter wrote:
> iommu_bus_init() registers a bus notifier on the given bus by using
> a statically defined notifier block:
> 
>   static struct notifier_block iommu_bus_nb = {
>           .notifier_call = iommu_bus_notifier,
>   };
> 
> This same notifier block is used for all busses. This causes a
> problem for notifiers registered after iommu has registered this
> callback on multiple busses. The problem is that a subsequent
> notifier being registered on a bus which has this iommu notifier
> will also get linked in to the notifier list of all other busses
> which have this iommu notifier.
> 
> This patch fixes this by allocating the notifier_block at runtime.
> Some error checking is also added to catch any allocation failure
> or notifier registration error.
> 
> Signed-off-by: Mark Salter <msalter@redhat.com>
> ---
>  drivers/iommu/iommu.c | 26 ++++++++++++++++----------
>  1 file changed, 16 insertions(+), 10 deletions(-)

Makes sense, applied. Where have you hit this condition where IOMMUs for
different buses are registered?


	Joerg

Re: [PATCH] iommu/core: fix bus notifier breakage

[Mark Salter]

On Thu, 2014-09-25 at 16:47 +0200, Joerg Roedel wrote:
> On Sun, Sep 21, 2014 at 01:58:24PM -0400, Mark Salter wrote:
> > iommu_bus_init() registers a bus notifier on the given bus by using
> > a statically defined notifier block:
> > 
> >   static struct notifier_block iommu_bus_nb = {
> >           .notifier_call = iommu_bus_notifier,
> >   };
> > 
> > This same notifier block is used for all busses. This causes a
> > problem for notifiers registered after iommu has registered this
> > callback on multiple busses. The problem is that a subsequent
> > notifier being registered on a bus which has this iommu notifier
> > will also get linked in to the notifier list of all other busses
> > which have this iommu notifier.
> > 
> > This patch fixes this by allocating the notifier_block at runtime.
> > Some error checking is also added to catch any allocation failure
> > or notifier registration error.
> > 
> > Signed-off-by: Mark Salter <msalter@redhat.com>
> > ---
> >  drivers/iommu/iommu.c | 26 ++++++++++++++++----------
> >  1 file changed, 16 insertions(+), 10 deletions(-)
> 
> Makes sense, applied. Where have you hit this condition where IOMMUs for
> different buses are registered?

arm_smmu_init()

	/* Oh, for a proper bus abstraction */
	if (!iommu_present(&platform_bus_type))
		bus_set_iommu(&platform_bus_type, &arm_smmu_ops);

#ifdef CONFIG_ARM_AMBA
	if (!iommu_present(&amba_bustype))
		bus_set_iommu(&amba_bustype, &arm_smmu_ops);
#endif

#ifdef CONFIG_PCI
	if (!iommu_present(&pci_bus_type))
		bus_set_iommu(&pci_bus_type, &arm_smmu_ops);
#endif