On Thu, Aug 22, 2024 at 11:45:55AM -0300, Jason Gunthorpe wrote:
> These three implementations of map_pages() all succeed if a mapping is
> requested with no read or write. Since they return back to __iommu_map()
> leaving the mapped output as 0 it triggers an infinite loop. Therefore
> nothing is using no-access protection bits.
>
> Further, VFIO and iommufd rely on iommu_iova_to_phys() to get back PFNs
> stored by map, if iommu_map() succeeds but iommu_iova_to_phys() fails that
> will create serious bugs.
>
> Thus remove this never used "nothing to do" concept and just fail map
> immediately.
>
> Fixes: e5fc9753b1a8 ("iommu/io-pgtable: Add ARMv7 short descriptor support")
> Fixes: e1d3c0fd701d ("iommu: add ARM LPAE page table allocator")
> Fixes: 745ef1092bcf ("iommu/io-pgtable: Move Apple DART support to its own file")
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
> drivers/iommu/io-pgtable-arm-v7s.c | 3 +--
> drivers/iommu/io-pgtable-arm.c | 3 +--
> drivers/iommu/io-pgtable-dart.c | 3 +--
> 3 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index 75f244a3e12df6..06ffc683b28fee 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -552,9 +552,8 @@ static int arm_v7s_map_pages(struct io_pgtable_ops *ops, unsigned long iova,
> paddr >= (1ULL << data->iop.cfg.oas)))
> return -ERANGE;
>
> - /* If no access, then nothing to do */
> if (!(prot & (IOMMU_READ | IOMMU_WRITE)))
> - return 0;
> + return -EINVAL;
>
> while (pgcount--) {
> ret = __arm_v7s_map(data, iova, paddr, pgsize, prot, 1, data->pgd,
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index f5d9fd1f45bf49..ff4149ae1751d4 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -515,9 +515,8 @@ static int arm_lpae_map_pages(struct io_pgtable_ops *ops, unsigned long iova,
> if (WARN_ON(iaext || paddr >> cfg->oas))
> return -ERANGE;
>
> - /* If no access, then nothing to do */
> if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
> - return 0;
> + return -EINVAL;
I think just removing this hunk altogether would get us the right semantics
for stage-2 mappings, but it's esoteric and not used so -EINVAL is probably
better:
Acked-by: Will Deacon <will@xxxxxxxxxx>
Will
