Re: [PATCH v2 0/3] iommufd: Fix vDEVICE allocation lifecycle bugs

[Pranjal Shrivastava]

On Sun, Jul 05, 2026 at 10:36:08PM -0700, Nicolin Chen wrote:
> Sashiko flagged a few bugs in how IOMMU_VDEVICE_ALLOC creates and validates
> a vDEVICE on a vIOMMU:
> 
>  - the core publishes a vDEVICE into the vIOMMU xarray before the driver's
>    vdevice_init() runs, so a concurrent invalidation can reach one it has
>    not yet accepted;
>  - the undersized-vdevice_size guard returns holding the igroup mutex,
>    deadlocking later vDEVICE operations on that group;
>  - the Arm SMMUv3 vIOMMU accepts a device without exactly one Stream ID:
>    an out-of-bounds streams[] read for none, stale ATC/IOTLB for several.
> 
> Fix each of them properly.
> 
> This is on Github:
> https://github.com/nicolinc/iommufd/commits/fix_vdevice_sashiko-v2
> 
> Changelog
> v2
>  * Add "Reviewed-by" from Kevin
>  * Patch-2: Add "Cc stable"; drop the out_release label by inlining the
>    xa_release() call
>  * Patch-2: Note that the reserved slot is hidden only via xa_* helpers
>  * Patch-3: Return -EOPNOTSUPP instead of -EINVAL
> v1
>  https://lore.kernel.org/all/cover.1782767110.git.nicolinc@xxxxxxxxxx/
> 
> Nicolin Chen (3):
>   iommufd/viommu: Release the igroup lock on the vdevice_size error path
>   iommufd/viommu: Publish a vDEVICE only after vdevice_init() succeeds
>   iommu/arm-smmu-v3-iommufd: Require exactly one Stream ID for a vDEVICE
> 
>  .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     | 15 +++++++++++++
>  drivers/iommu/iommufd/viommu.c                | 22 ++++++++++++++-----
>  2 files changed, 31 insertions(+), 6 deletions(-)
> 

Reviewed-by: Pranjal Shrivastava <praan@xxxxxxxxxx>

Thanks,
Praan