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

Will Deacon
2017-08-08T11:21:44Z

[+ 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) {
> >
>