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[PATCH] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device

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  [PATCH] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device Artem Savkov <asavkov@redhat.com> - 2017-08-08 11:00 +0200
    Re: [PATCH] iommu/arm-smmu: fix null-pointer dereference in  arm_smmu_add_device Will Deacon <will.deacon@arm.com> - 2017-08-08 11:30 +0200
      [PATCH v2] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device Artem Savkov <asavkov@redhat.com> - 2017-08-08 12:30 +0200
        Re: [PATCH v2] iommu/arm-smmu: fix null-pointer dereference in  arm_smmu_add_device Robin Murphy <robin.murphy@arm.com> - 2017-08-08 12:40 +0200
          Re: [PATCH v2] iommu/arm-smmu: fix null-pointer dereference in  arm_smmu_add_device Will Deacon <will.deacon@arm.com> - 2017-08-08 13:30 +0200

#1706198 — [PATCH] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device

Commit c54451a "iommu/arm-smmu: Fix the error path in arm_smmu_add_device"
removed fwspec assignment in legacy_binding path as redundant which is
wrong. It needs to be updated after fwspec initialisation in
arm_smmu_register_legacy_master() as it is dereferenced later. Without
this there is a NULL-pointer dereference panic during boot on some hosts.

Signed-off-by: Artem Savkov <asavkov@redhat.com>
---
 drivers/iommu/arm-smmu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index b97188a..95f1c86 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1519,6 +1519,7 @@ static int arm_smmu_add_device(struct device *dev)
 
 	if (using_legacy_binding) {
 		ret = arm_smmu_register_legacy_master(dev, &smmu);
+		fwspec = dev->iommu_fwspec;
 		if (ret)
 			goto out_free;
 	} else if (fwspec && fwspec->ops == &arm_smmu_ops) {
-- 
2.7.5

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#1706253 — Re: [PATCH] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device

Hi Artem,

Thanks for the patch.

On Tue, Aug 08, 2017 at 10:58:01AM +0200, Artem Savkov wrote:
> Commit c54451a "iommu/arm-smmu: Fix the error path in arm_smmu_add_device"
> removed fwspec assignment in legacy_binding path as redundant which is
> wrong. It needs to be updated after fwspec initialisation in
> arm_smmu_register_legacy_master() as it is dereferenced later. Without
> this there is a NULL-pointer dereference panic during boot on some hosts.
> 
> Signed-off-by: Artem Savkov <asavkov@redhat.com>
> ---
>  drivers/iommu/arm-smmu.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index b97188a..95f1c86 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1519,6 +1519,7 @@ static int arm_smmu_add_device(struct device *dev)
>  
>  	if (using_legacy_binding) {
>  		ret = arm_smmu_register_legacy_master(dev, &smmu);
> +		fwspec = dev->iommu_fwspec;
>  		if (ret)
>  			goto out_free;
>  	} else if (fwspec && fwspec->ops == &arm_smmu_ops) {

Damn, you're completely right! Robin and I bashed our heads against this for
a while and couldn't remember why the code was structured like it was, but
that explains it. Can you add a comment saying that
arm_smmu_register_legacy_master will allocate an fwspec if its initially NULL,
please?

Cheers,

Will

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#1706297 — [PATCH v2] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device

Commit c54451a "iommu/arm-smmu: Fix the error path in arm_smmu_add_device"
removed fwspec assignment in legacy_binding path as redundant which is
wrong. It needs to be updated after fwspec initialisation in
arm_smmu_register_legacy_master() as it is dereferenced later. Without
this there is a NULL-pointer dereference panic during boot on some hosts.

Signed-off-by: Artem Savkov <asavkov@redhat.com>
---
 drivers/iommu/arm-smmu.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index b97188a..2d80fa8 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1519,6 +1519,13 @@ static int arm_smmu_add_device(struct device *dev)
 
 	if (using_legacy_binding) {
 		ret = arm_smmu_register_legacy_master(dev, &smmu);
+
+		/*
+		 * If dev->iommu_fwspec is initally NULL, arm_smmu_register_legacy_master()
+		 * will allocate/initialise a new one. Thus we need to update fwspec for
+		 * later use.
+		 */
+		fwspec = dev->iommu_fwspec;
 		if (ret)
 			goto out_free;
 	} else if (fwspec && fwspec->ops == &arm_smmu_ops) {
-- 
2.7.5

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#1706308 — Re: [PATCH v2] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device

On 08/08/17 11:26, Artem Savkov wrote:
> Commit c54451a "iommu/arm-smmu: Fix the error path in arm_smmu_add_device"
> removed fwspec assignment in legacy_binding path as redundant which is
> wrong. It needs to be updated after fwspec initialisation in
> arm_smmu_register_legacy_master() as it is dereferenced later. Without
> this there is a NULL-pointer dereference panic during boot on some hosts.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

Thanks for fixing it up, and sorry for failing to document the
unfortunately subtle logic in the first place!

Robin.

> Signed-off-by: Artem Savkov <asavkov@redhat.com>
> ---
>  drivers/iommu/arm-smmu.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index b97188a..2d80fa8 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1519,6 +1519,13 @@ static int arm_smmu_add_device(struct device *dev)
>  
>  	if (using_legacy_binding) {
>  		ret = arm_smmu_register_legacy_master(dev, &smmu);
> +
> +		/*
> +		 * If dev->iommu_fwspec is initally NULL, arm_smmu_register_legacy_master()
> +		 * will allocate/initialise a new one. Thus we need to update fwspec for
> +		 * later use.
> +		 */
> +		fwspec = dev->iommu_fwspec;
>  		if (ret)
>  			goto out_free;
>  	} else if (fwspec && fwspec->ops == &arm_smmu_ops) {
> 

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#1706376 — Re: [PATCH v2] iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device

[+ Joerg]

On Tue, Aug 08, 2017 at 11:37:40AM +0100, Robin Murphy wrote:
> On 08/08/17 11:26, Artem Savkov wrote:
> > Commit c54451a "iommu/arm-smmu: Fix the error path in arm_smmu_add_device"
> > removed fwspec assignment in legacy_binding path as redundant which is
> > wrong. It needs to be updated after fwspec initialisation in
> > arm_smmu_register_legacy_master() as it is dereferenced later. Without
> > this there is a NULL-pointer dereference panic during boot on some hosts.
> 
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> 
> Thanks for fixing it up, and sorry for failing to document the
> unfortunately subtle logic in the first place!

Well, I was the one that messed it up:

Acked-by: Will Deacon <will.deacon@arm.com>

Joerg, can you pick this up as a fix for 4.13, please?

Will

> > Signed-off-by: Artem Savkov <asavkov@redhat.com>
> > ---
> >  drivers/iommu/arm-smmu.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> > index b97188a..2d80fa8 100644
> > --- a/drivers/iommu/arm-smmu.c
> > +++ b/drivers/iommu/arm-smmu.c
> > @@ -1519,6 +1519,13 @@ static int arm_smmu_add_device(struct device *dev)
> >  
> >  	if (using_legacy_binding) {
> >  		ret = arm_smmu_register_legacy_master(dev, &smmu);
> > +
> > +		/*
> > +		 * If dev->iommu_fwspec is initally NULL, arm_smmu_register_legacy_master()
> > +		 * will allocate/initialise a new one. Thus we need to update fwspec for
> > +		 * later use.
> > +		 */
> > +		fwspec = dev->iommu_fwspec;
> >  		if (ret)
> >  			goto out_free;
> >  	} else if (fwspec && fwspec->ops == &arm_smmu_ops) {
> > 
> 

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