diff --git a/mm/mmap.c b/mm/mmap.c
index 772140c..f2f03df 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1114,6 +1114,8 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 }
 EXPORT_SYMBOL(do_mmap_pgoff);
 
+DEFINE_MUTEX(mmap_sem_mutex);
+
 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 		unsigned long, prot, unsigned long, flags,
 		unsigned long, fd, unsigned long, pgoff)
@@ -1145,9 +1147,11 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 
 	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
 
+	mutex_lock(&mmap_sem_mutex);
 	down_write(&current->mm->mmap_sem);
 	retval = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
 	up_write(&current->mm->mmap_sem);
+	mutex_unlock(&mmap_sem_mutex);
 
 	if (file)
 		fput(file);
@@ -2149,9 +2153,11 @@ SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
 
 	profile_munmap(addr);
 
+	mutex_lock(&mmap_sem_mutex);
 	down_write(&mm->mmap_sem);
 	ret = do_munmap(mm, addr, len);
 	up_write(&mm->mmap_sem);
+	mutex_unlock(&mmap_sem_mutex);
 	return ret;
 }