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

Robin Murphy
2017-08-08T10:37:45Z

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) {
>