[v2 PATCH] iommu/arm-smmu-v3: Fix L1 stream table index calculation for 32-bit sid size
Yang Shi
yang at os.amperecomputing.com
Fri Oct 4 09:37:10 PDT 2024
On 10/4/24 9:29 AM, Yang Shi wrote:
>
>
> 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.
The size parameter passed to dmam_alloc_coherent() is size_t type. We
may do:
+#define SIZE_4G (4 * 1024 * 1024 * 1024ULL)
+
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;
+ u64 num_sids;
/* It is not practical to have too large stream id size for
linear */
if (smmu->sid_bits > 31)
@@ -3667,6 +3669,9 @@ static int arm_smmu_init_strtab_linear(struct
arm_smmu_device *smmu)
num_sids = arm_smmu_strtab_num_sids(smmu);
size = num_sids * sizeof(struct arm_smmu_ste);
+ if (size > SIZE_4G)
+ return -EINVAL;
+
cfg->linear.table = dmam_alloc_coherent(smmu->dev, size,
&cfg->linear.ste_dma,
GFP_KERNEL);
>
>>
>> Jason
>
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