iommu/amd: Remove amd_iommu_domain_update() from page table freeing

It is a serious bug if the domain is still mapped to any DTEs when it is
freed as we immediately start freeing page table memory, so any remaining
HW touch will UAF.

If it is not mapped then dev_list is empty and amd_iommu_domain_update()
does nothing.

Remove it and add a WARN_ON() to catch this class of bug.

Reviewed-by: Vasant Hegde <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

Author: jgunthorpe

drivers/iommu/amd/io_pgtable.c

@@ -577,9 +577,6 @@ static void v1_free_pgtable(struct io_pgtable *iop)
 
 	/* Update data structure */
 	amd_iommu_domain_clr_pt_root(dom);
-
-	/* Make changes visible to IOMMUs */
-	amd_iommu_domain_update(dom);
 }
 
 static struct io_pgtable *v1_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)

drivers/iommu/amd/iommu.c

@@ -2255,6 +2255,8 @@ void protection_domain_free(struct protection_domain *domain)
 	if (!domain)
 		return;
 
+	WARN_ON(!list_empty(&domain->dev_list));
+
 	if (domain->iop.pgtbl_cfg.tlb)
 		free_io_pgtable_ops(&domain->iop.iop.ops);