--- a/vmnet/Makefile
+++ b/vmnet/Makefile
@@ -43,7 +43,11 @@ INCLUDE      += -I$(SRCROOT)/shared
 endif
 
 
+ifdef KVERSION
+VM_UNAME = $(KVERSION)
+else
 VM_UNAME = $(shell uname -r)
+endif
 
 # Header directory for the running kernel
 ifdef LINUXINCLUDE
@@ -98,6 +98,13 @@ auto-build: $(DRIVER_KO)
 $(DRIVER): $(DRIVER_KO)
 	if [ $< -nt $@ ] || [ ! -e $@ ] ; then cp -f $< $@; fi
 
+# Use SUBDIRS on 2.x, 3.x, 4.x.  Use M on newer kernels.
+ifeq ($(filter-out 2 3 4,$(firstword $(subst ., ,$(VM_UNAME)))),)
+DIRVAR := SUBDIRS
+else
+DIRVAR := M
+endif
+
 #
 # Define a setup target that gets built before the actual driver.
 # This target may not be used at all, but if it is then it will be defined
@@ -107,7 +114,7 @@ prebuild:: ;
 postbuild:: ;
 
 $(DRIVER_KO): prebuild
-	$(MAKE) -C $(BUILD_DIR) SUBDIRS=$$PWD SRCROOT=$$PWD/$(SRCROOT) \
+	$(MAKE) -C $(BUILD_DIR) $(DIRVAR)=$$PWD SRCROOT=$$PWD/$(SRCROOT) \
 	  MODULEBUILDDIR=$(MODULEBUILDDIR) modules
 	$(MAKE) -C $$PWD SRCROOT=$$PWD/$(SRCROOT) \
 	  MODULEBUILDDIR=$(MODULEBUILDDIR) postbuild
--- a/vmnet/userif.c
+++ b/vmnet/userif.c
@@ -137,16 +137,21 @@
  */
 
 static INLINE int
-VNetUserIfMapPtr(VA uAddr,        // IN: pointer to user memory
+VNetUserIfMapPtr(VA64 uAddr,      // IN: pointer to user memory
                  size_t size,     // IN: size of data
                  struct page **p, // OUT: locked page
                  void **ptr)      // OUT: kernel mapped pointer
 {
-   if (!access_ok(VERIFY_WRITE, (void *)uAddr, size) ||
-       (((uAddr + size - 1) & ~(PAGE_SIZE - 1)) !=
-        (uAddr & ~(PAGE_SIZE - 1)))) {
+   uint8 v;
+
+   /* Check area does not straddle two pages. */
+   if ((uAddr & (PAGE_SIZE - 1)) + size > PAGE_SIZE) {
       return -EINVAL;
    }
+   /* Check if it is user's area.  UserifLockPage() checks writability. */
+   if (copy_from_user(&v, (void *)(unsigned long)uAddr, sizeof v) != 0) {
+      return -EFAULT;
+   }
 
    *p = UserifLockPage(uAddr);
    if (*p == NULL) {
@@ -158,7 +163,7 @@
 }
 
 static INLINE int
-VNetUserIfMapUint32Ptr(VA uAddr,        // IN: pointer to user memory
+VNetUserIfMapUint32Ptr(VA64 uAddr,      // IN: pointer to user memory
                        struct page **p, // OUT: locked page
                        uint32 **ptr)    // OUT: kernel mapped pointer
 {
@@ -201,7 +206,7 @@
       return -EBUSY;
    }
 
-   if ((retval = VNetUserIfMapUint32Ptr((VA)vn->pollPtr, &pollPage,
+   if ((retval = VNetUserIfMapUint32Ptr(vn->pollPtr, &pollPage,
                                         &pollPtr)) < 0) {
       return retval;
    }
@@ -213,7 +218,7 @@
       goto error_free;
    }
 
-   if ((retval = VNetUserIfMapUint32Ptr((VA)vn->recvClusterPtr,
+   if ((retval = VNetUserIfMapUint32Ptr(vn->recvClusterPtr,
                                         &recvClusterPage,
                                         &recvClusterCount)) < 0) {
       goto error_free;