iommufd: Do not allow creating areas without READ or WRITE

This results in passing 0 or just IOMMU_CACHE to iommu_map(). Most of
the page table formats don't like this:

  amdv1 - -EINVAL
  armv7s - returns 0, doesn't update mapped
  arm-lpae - returns 0 doesn't update mapped
  dart - returns 0, doesn't update mapped
  VT-D - returns -EINVAL

Unfortunately the three formats that return 0 cause serious problems:

 - Returning ret = but not uppdating mapped from domain->map_pages()
   causes an infinite loop in __iommu_map()

 - Not writing ioptes means that VFIO/iommufd have no way to recover them
   and we will have memory leaks and worse during unmap

Since almost nothing can support this, and it is a useless thing to do,
block it early in iommufd.

Cc: [email protected]
Fixes: aad37e7 ("iommufd: IOCTLs for the io_pagetable")
Signed-off-by: Jason Gunthorpe <[email protected]>
Reviewed-by: Nicolin Chen <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

Author: jgunthorpe

drivers/iommu/iommufd/ioas.c

@@ -213,6 +213,10 @@ int iommufd_ioas_map(struct iommufd_ucmd *ucmd)
 	if (cmd->iova >= ULONG_MAX || cmd->length >= ULONG_MAX)
 		return -EOVERFLOW;
 
+	if (!(cmd->flags &
+	      (IOMMU_IOAS_MAP_WRITEABLE | IOMMU_IOAS_MAP_READABLE)))
+		return -EINVAL;
+
 	ioas = iommufd_get_ioas(ucmd->ictx, cmd->ioas_id);
 	if (IS_ERR(ioas))
 		return PTR_ERR(ioas);
@@ -253,6 +257,10 @@ int iommufd_ioas_copy(struct iommufd_ucmd *ucmd)
 	    cmd->dst_iova >= ULONG_MAX)
 		return -EOVERFLOW;
 
+	if (!(cmd->flags &
+	      (IOMMU_IOAS_MAP_WRITEABLE | IOMMU_IOAS_MAP_READABLE)))
+		return -EINVAL;
+
 	src_ioas = iommufd_get_ioas(ucmd->ictx, cmd->src_ioas_id);
 	if (IS_ERR(src_ioas))
 		return PTR_ERR(src_ioas);

tools/testing/selftests/iommu/iommufd.c

@@ -825,7 +825,7 @@ TEST_F(iommufd_ioas, copy_area)
 {
 	struct iommu_ioas_copy copy_cmd = {
 		.size = sizeof(copy_cmd),
-		.flags = IOMMU_IOAS_MAP_FIXED_IOVA,
+		.flags = IOMMU_IOAS_MAP_FIXED_IOVA | IOMMU_IOAS_MAP_WRITEABLE,
 		.dst_ioas_id = self->ioas_id,
 		.src_ioas_id = self->ioas_id,
 		.length = PAGE_SIZE,
@@ -1318,7 +1318,7 @@ TEST_F(iommufd_ioas, copy_sweep)
 {
 	struct iommu_ioas_copy copy_cmd = {
 		.size = sizeof(copy_cmd),
-		.flags = IOMMU_IOAS_MAP_FIXED_IOVA,
+		.flags = IOMMU_IOAS_MAP_FIXED_IOVA | IOMMU_IOAS_MAP_WRITEABLE,
 		.src_ioas_id = self->ioas_id,
 		.dst_iova = MOCK_APERTURE_START,
 		.length = MOCK_PAGE_SIZE,
@@ -1608,7 +1608,7 @@ TEST_F(iommufd_mock_domain, user_copy)
 	};
 	struct iommu_ioas_copy copy_cmd = {
 		.size = sizeof(copy_cmd),
-		.flags = IOMMU_IOAS_MAP_FIXED_IOVA,
+		.flags = IOMMU_IOAS_MAP_FIXED_IOVA | IOMMU_IOAS_MAP_WRITEABLE,
 		.dst_ioas_id = self->ioas_id,
 		.dst_iova = MOCK_APERTURE_START,
 		.length = BUFFER_SIZE,