[PATCH v7 13/28] iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE_ALLOC ioctl

[Jason Gunthorpe]

On Fri, Jul 04, 2025 at 10:26:02AM -0300, Jason Gunthorpe wrote:

> /* DIV_ROUND_UP(offset + cmd->length, PAGE_SIZE) */
> if (check_add_overflow(offset, cmd->length, &length))
>    return -ERANGE;
> if (check_add_overflow(length, PAGE_SIZE-1, &length))
>    return -ERANGE;
> if (length > SIZE_MAX)
>    return -ERANGE;
> max_npages = length / PAGE_SIZE;

Actually I see now that overflow.h supports mixed types, so this can
be simplified:

 size_t max_npages;
 size_t length;
 u64 offset;
 size_t i;

 offset = cmd->nesting_parent_iova - PAGE_ALIGN(cmd->nesting_parent_iova);

 /* DIV_ROUND_UP(offset + cmd->length, PAGE_SIZE) */
 if (check_add_overflow(offset, cmd->length, &length))
    return -ERANGE;
 if (check_add_overflow(length, PAGE_SIZE-1, &length))
    return -ERANGE;
 max_npages = length / PAGE_SIZE;

Then the kcvalloc takes in size_t:

kvmalloc_array_node_noprof(size_t n, size_t size, gfp_t flags, int node)

So there is no silent cast and truncation.

Jason