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

[David Daney]

On 08/08/2017 04:21 AM, Will Deacon wrote:
> [+ 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@xxxxxxx>
> >
> > 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@xxxxxxx>
>
> Joerg, can you pick this up as a fix for 4.13, please?

I hit the Oops as well.  This patch fixes it for me on a Cavium CN88xx 
system, so:

Acked-by: David Daney <david.daney@xxxxxxxxxx>

Thanks for working on this.



> Will
>
> > > Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
> > > ---
> > >   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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