Re: [PATCH] vfio: Fix ksize arg while copying user struct in vfio_df_ioctl_bind_iommufd()

[liulongfang <liulongfang@huawei.com>]

On 2025/11/1 1:09, Raghavendra Rao Ananta wrote:
> On Thu, Oct 30, 2025 at 6:34 PM liulongfang <liulongfang@huawei.com> wrote:
>>
>> On 2025/10/31 1:12, Raghavendra Rao Ananta wrote:
>>> For the cases where user includes a non-zero value in 'token_uuid_ptr'
>>> field of 'struct vfio_device_bind_iommufd', the copy_struct_from_user()
>>> in vfio_df_ioctl_bind_iommufd() fails with -E2BIG. For the 'minsz' passed,
>>> copy_struct_from_user() expects the newly introduced field to be zero-ed,
>>> which would be incorrect in this case.
>>>
>>> Fix this by passing the actual size of the kernel struct. If working
>>> with a newer userspace, copy_struct_from_user() would copy the
>>> 'token_uuid_ptr' field, and if working with an old userspace, it would
>>> zero out this field, thus still retaining backward compatibility.
>>>
>>> Fixes: 86624ba3b522 ("vfio/pci: Do vf_token checks for VFIO_DEVICE_BIND_IOMMUFD")
>>
>> Hi Ananta,
>>
>> This patch also has another bug: in the hisi_acc_vfio_pci.c driver, It have two "struct vfio_device_ops"
>> Only one of them, "hisi_acc_vfio_pci_ops" has match_token_uuid added,
>> while the other one, "hisi_acc_vfio_pci_migrn_ops", is missing it.
>> This will cause a QEMU crash (call trace) when QEMU tries to start the device.
>>
>> Could you please help include this fix in your patchset as well?
>>
>> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> @@ -1637,6 +1637,7 @@ static const struct vfio_device_ops hisi_acc_vfio_pci_migrn_ops = {
>>         .mmap = hisi_acc_vfio_pci_mmap,
>>         .request = vfio_pci_core_request,
>>         .match = vfio_pci_core_match,
>> +       .match_token_uuid = vfio_pci_core_match_token_uuid,
>>         .bind_iommufd = vfio_iommufd_physical_bind,
>>         .unbind_iommufd = vfio_iommufd_physical_unbind,
>>         .attach_ioas = vfio_iommufd_physical_attach_ioas,
>>
> Sent as a separate patch in v2:
> https://lore.kernel.org/all/20251031170603.2260022-3-rananta@google.com/
> (untested).
>

I've tested this patch locally, and after applying it, QEMU no longer fails to start
and the functionality works as expected.

Thanks.
Longfang.

> Thank you.
> Raghavendra
> .
>