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

David Daney
2017-08-09T21:41:57Z

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@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?

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

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

Thanks for working on this.

>
> 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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