Re: [v2 PATCH] iommu/arm-smmu-v3: Fix L1 stream table index calculation for 32-bit sid size

[Yang Shi <yang@os.amperecomputing.com>]

On 10/4/24 9:14 AM, Jason Gunthorpe wrote:
> On Fri, Oct 04, 2024 at 09:05:46AM -0700, Yang Shi wrote:
>>
>> On 10/4/24 5:43 AM, Jason Gunthorpe wrote:
>>> On Thu, Oct 03, 2024 at 08:31:23AM -0700, Yang Shi wrote:
>>>> If I understand correctly, the check is mainly used to avoid the u64 -> u32
>>>> overflow. This check guarantee no overflow. If some crazy hardware really
>>>> requests that large memory, the allocation will fail.
>>> Sure, the kalloc will print a warn on anyhow if it is too big
>> Thank you. Will spin a new revision.
> Oh wait a sec, it is not so simple, the 31 is too big because the
> multiply will overflow or truncate to size_t too. This is why I picked
> something lower.

How about define the size as u64?

  static int arm_smmu_init_strtab_linear(struct arm_smmu_device *smmu)
  {
-       u32 size;
+       u64 size;
         struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
         u32 num_sids;

It won't overflow and the large allocation will fail anyway.

>
> Jason