diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
index b30f34a..db2d885 100644
--- a/arch/um/include/asm/Kbuild
+++ b/arch/um/include/asm/Kbuild
@@ -3,3 +3,4 @@ generic-y += hw_irq.h irq_regs.h kdebug.h percpu.h sections.h topology.h xor.h
 generic-y += ftrace.h pci.h io.h param.h delay.h mutex.h current.h exec.h
 generic-y += switch_to.h clkdev.h
 generic-y += trace_clock.h
+header-y += mman.h
diff --git a/arch/um/include/asm/mman.h b/arch/um/include/asm/mman.h
new file mode 100644
index 0000000..d8fb362
--- /dev/null
+++ b/arch/um/include/asm/mman.h
@@ -0,0 +1,10 @@
+#ifndef __UM_MMAN_H__
+#define __UM_MMAN_H__
+
+#include <uapi/asm/mman.h>
+#include <as-layout.h>
+
+#define arch_mmap_check(addr, len, flags) \
+	(((flags) & MAP_FIXED && (addr) < STUB_START + STUB_END) ? -EINVAL : 0)
+
+#endif /* __UM_MMAN_H__ */
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index ff03067..db09322 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -103,7 +103,7 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
 
 void uml_setup_stubs(struct mm_struct *mm)
 {
-	int err, ret;
+	int ret;
 
 	if (!skas_needs_stub)
 		return;
@@ -120,15 +120,10 @@ void uml_setup_stubs(struct mm_struct *mm)
 	mm->context.stub_pages[0] = virt_to_page(&__syscall_stub_start);
 	mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
 
-	/* dup_mmap already holds mmap_sem */
-	err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
-				      VM_READ | VM_MAYREAD | VM_EXEC |
-				      VM_MAYEXEC | VM_DONTCOPY,
-				      mm->context.stub_pages);
-	if (err) {
-		printk(KERN_ERR "install_special_mapping returned %d\n", err);
-		goto out;
-	}
+	/* XXX: the stub pages don't have a VMA, ensure that the PTR counter
+	 * is correct at process exit. */
+	mm->nr_ptes--;
+
 	return;
 
 out: