diff --git a/mm/memory.c b/mm/memory.c
index ec63dd6212ac..926276d41920 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -7131,6 +7131,12 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
 	bool writable;
 	struct follow_pfnmap_args args = { .vma = vma, .address = addr };
 
+	/*
+	 * Limit access to one page at a time, as that's what follow_pfnmap_start()
+	 * guarantees; expect the caller to retry to read larger ranges.
+	 */
+	len = min_t(int, len, PAGE_SIZE - offset);
+
 retry:
 	if (follow_pfnmap_start(&args))
 		return -EINVAL;
@@ -7142,7 +7148,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
 	if ((write & FOLL_WRITE) && !writable)
 		return -EINVAL;
 
-	maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot);
+	maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
 	if (!maddr)
 		return -ENOMEM;
 
@@ -7150,7 +7156,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
 		goto out_unmap;
 
 	if ((pgprot_val(prot) != pgprot_val(args.pgprot)) ||
-	    (phys_addr != (args.pfn << PAGE_SHIFT)) ||
+	    (phys_addr != ((resource_size_t)args.pfn << PAGE_SHIFT)) ||
 	    (writable != args.writable)) {
 		follow_pfnmap_end(&args);
 		iounmap(maddr);