Re: [PATCH v8 13/15] iommu/amd: Use the generic iommu page table

Alejandro Jimenez
2025-12-05T20:08:49Z

On 12/5/25 2:46 PM, Jason Gunthorpe wrote:
> On Fri, Dec 05, 2025 at 10:40:49AM +0800, Lai, Yi wrote:
>> Hi Alejandro Jimenez,
>>
>> Greetings!
>>
>> I used Syzkaller and found that there is WARNING in iommufd_fops_release in linux-next next-20251203.
>>
>> After bisection and the first bad commit is:
>> "
>> 789a5913b29c iommu/amd: Use the generic iommu page table
>> "
>
> This bisect didn't work out, it is close, but the commit is
>

Thank you Jason for debugging this. I was wondering what could be the
possible relation with the AMD changes, since the commit doesn't touch
iommufd/main.c, and the syskaller logs show Intel HW so the AMD driver
code is not involved.

Thank you,
Alejandro

> e93d5945ed5b ("iommufd: Change the selftest to use iommupt instead of xarray")
>
> It is a refcount leak:
>
> @@ -1215,8 +1215,10 @@ static int iommufd_test_md_check_pa(struct iommufd_ucmd *ucmd,
> page_size = 1 << __ffs(mock->domain.pgsize_bitmap);
> if (iova % page_size || length % page_size ||
> (uintptr_t)uptr % page_size ||
> - check_add_overflow((uintptr_t)uptr, (uintptr_t)length, &end))
> - return -EINVAL;
> + check_add_overflow((uintptr_t)uptr, (uintptr_t)length, &end)) {
> + rc = -EINVAL;
> + goto out_put;
> + }
>
> I'll send a patch, thanks
>
> Jason