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SubjectRe: [PATCH V1 1/1] iommu: Make sure device's ID array elements are unique
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On 19.12.2017 17:37, Alex Williamson wrote:
> On Tue, 19 Dec 2017 16:20:21 +0100
> Tomasz Nowicki <tomasz.nowicki@caviumnetworks.com> wrote:
>
>> While iterating over DMA aliases for a PCI device, for some rare cases
>> (i.e. PCIe-to-PCI/X bridges) we may get exactly the same ID as initial child
>> device. In turn, the same ID may get registered for a device multiple times.
>> Eventually IOMMU driver may try to configure the same ID within domain
>> multiple times too which for some IOMMU drivers is illegal and causes kernel
>> panic.
>>
>> Rule out ID duplication prior to device ID array registration.
>>
>> CC: stable@vger.kernel.org # v4.14+
>
> You've identified a release, is there a specific commit this fixes?

Yes, it was triggered by converting drm_pci_init() to
pci_register_driver() in ast_drv.c

Fixes: 10631d724def ("drm/pci: Deprecate drm_pci_init/exit completely
")

>
>> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@caviumnetworks.com>
>> ---
>> drivers/iommu/iommu.c | 28 ++++++++++++++++++++++++++++
>> 1 file changed, 28 insertions(+)
>>
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 3de5c0b..9b2c138 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -1945,6 +1945,31 @@ void iommu_fwspec_free(struct device *dev)
>> }
>> EXPORT_SYMBOL_GPL(iommu_fwspec_free);
>>
>> +static void iommu_fwspec_remove_ids_dup(struct device *dev, u32 *ids,
>> + int *num_ids)
>> +{
>> + struct iommu_fwspec *fwspec = dev->iommu_fwspec;
>> + int i, j, k, valid_ids = *num_ids;
>> +
>> + for (i = 0; i < valid_ids; i++) {
>> + for (j = 0; j < fwspec->num_ids; j++) {
>> + if (ids[i] != fwspec->ids[j])
>> + continue;
>> +
>> + dev_info(dev, "found 0x%x ID duplication, skipped\n",
>> + ids[i]);
>> +
>> + for (k = i + 1; k < valid_ids; k++)
>> + ids[k - 1] = ids[k];
>
> Use memmove()?

Right.

>
>> +
>> + valid_ids--;
>> + break;
>
> At this point ids[i] is not the ids[i] that we tested for dupes, it's
> what was ids[i + 1], but we're going to i++ on the next iteration and
> we therefore never test that entry.

Good point.

Now the fundamental question is where we should put the patch, here or
in SMMUv3 driver as per Robin suggestion.

Thanks,
Tomasz

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