Step 1: 
Here are five possible patches for the vulnerability based on line 16 of the code slice:

Patch 1:
```diff
- void *kern_buf;
+ char kern_buf[MAX_BUFFER_SIZE];

 static ssize_t
 bnad_debugfs_write_regrd(struct file *file, const char __user *buf,
@@ -16,7 +17,7 @@ static ssize_t bnad_debugfs_wri
 	kern_buf = memdup_user(buf, nbytes);

 }
-```
+}
+```

Patch 2:
```diff
 static ssize_t
 bnad_debugfs_write_regrd(struct file *file, const char __user *buf,
 @@ -16,7 +17,8 @@ static ssize_t bnad_debugfs_wri
 	void *kern_buf;

-	kern_buf = memdup_user(buf, nbytes);
+	if (nbytes > MAX_BUFFER_SIZE) {
+		return -ENOMEM;
+	}
+	kern_buf = memdup_user(buf, nbytes);

 }
```

Patch 3:
```diff
 static ssize_t
 bnad_debugfs_write_regrd(struct file *file, const char __user *buf,
-	size_t nbytes, loff_t *ppos)
+	size_t nbytes, loff_t *ppos, size_t max_size)
 	void *kern_buf;

+	if (nbytes > max_size) {
+		return -ENOMEM;
+	}
+
-	kern_buf = memdup_user(buf, nbytes);
+	kern_buf = memdup_user(buf, nbytes);

 }
```

Patch 4:
```diff
 static ssize_t
 bnad_debugfs_write_regrd(struct file *file, const char __user *buf,
-	size_t nbytes, loff_t *ppos)
+	size_t nbytes, loff_t *ppos, size_t max_size)
 	void *kern_buf;

-	kern_buf = memdup_user(buf, nbytes);
+	if (nbytes > MAX_BUFFER_SIZE) {
+		return -ENOMEM;
+	}
+	kern_buf = memdup_user(buf, nbytes);

 }
```

Patch 5:
```diff
 static ssize_t
 bnad_debugfs_write_regrd(struct file *file, const char __user *buf,
-	size_t nbytes, loff_t *ppos)
+	size_t nbytes, loff_t *ppos, size_t max_size)
 	void *kern_buf;

-	kern_buf = memdup_user(buf, nbytes);
+	if (nbytes > MAX_BUFFER_SIZE || !capable(CAP_SYSADMIN)) {
+		return -ENOMEM;
+	}
+	kern_buf = memdup_user(buf, nbytes);

 }
```