powerpc/iommu: Fix the overflow validation in iommu_tce_check_ioba

In the Linux kernel, the following vulnerability has been resolved: powerpc/iommu: Fix the overflow validation in iommu_tce_check_ioba The commit b1af23d836f8 ("KVM: PPC: iommu: Unify TCE checking") unified IOBA parameter checking across KVM and VFIO into iommu_tce_check_ioba(). While doing so, the passed in argument npages is ignored and constant value '1' is used leaving out a possible overflow as the callers can legitimately be using npages > 1 for H_STUFF_TCE or H_PUT_TCE_INDIRECT cases. Fix this by accounting for 'npages', checking for arithmetic overflow, and verifying that the entire requested range (ioba - offset + npages) does not exceed the table capacity 'size'.

Where it's fixed