Re: [PATCH] iommu/s390: Fix NULL dereference in iova_to_phys() with ZPCI_TABLE_TYPE_RFX

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 8/18/26 3:13 PM, Niklas Schnelle wrote:
> When using a 5-level translation table via ZPCI_TABLE_TYPE_RFX
> get_rso_from_iova() returns NULL when the region-first entry is invalid.
> Yet in get_rto_from_iova() the region-second origin rso is not checked
> to be non-NULL before accessing rso[rsx] leading to a NULL pointer
> dereference instead of a NULL return when iova_to_phys() is called on
> a unmapped IOVA. Fix this by adding the missing NULL check.
> 
> Cc: stable@vger.kernel.org
> Fixes: 81244074b518 ("iommu/s390: allow larger region tables")
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>

> ---
>  drivers/iommu/s390-iommu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
> index f148f559ac56..58ca7727b7f2 100644
> --- a/drivers/iommu/s390-iommu.c
> +++ b/drivers/iommu/s390-iommu.c
> @@ -974,6 +974,8 @@ static unsigned long *get_rto_from_iova(struct s390_domain *domain,
>  	case ZPCI_TABLE_TYPE_RFX:
>  	case ZPCI_TABLE_TYPE_RSX:
>  		rso = get_rso_from_iova(domain, iova);
> +		if (!rso)
> +			return NULL;
>  		rsx = calc_rsx(iova);
>  		rse = READ_ONCE(rso[rsx]);
>  		if (!reg_entry_isvalid(rse))
> 
> ---
> base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f
> change-id: 20260818-iommu_fix_iova_to_phys-5879275b95ec
> 
> Best regards,