Q: Given the following code slice:
```
1 static ssize_t
2 bnad_debugfs_write_regrd(struct file *file, const char __user *buf,
3 		size_t nbytes, loff_t *ppos)
4 {
5 	struct bnad_debug_info *regrd_debug = file->private_data;
6 	struct bnad *bnad = (struct bnad *)regrd_debug->i_private;
7 	struct bfa_ioc *ioc = &bnad->bna.ioceth.ioc;
8 	int rc, i;
9 	u32 addr, len;
10 	u32 *regbuf;
11 	void __iomem *rb, *reg_addr;
12 	unsigned long flags;
13 	void *kern_buf;
14 
15 	/* Copy the user space buf */
16 	kern_buf = memdup_user(buf, nbytes);
17 	if (IS_ERR(kern_buf))
18 		return PTR_ERR(kern_buf);
19 
20 	rc = sscanf(kern_buf, "%x:%x", &addr, &len);
21 	if (rc < 2 || len > UINT_MAX >> 2) {
22 		netdev_warn(bnad->netdev, "failed to read user buffer\n");
23 		kfree(kern_buf);
24 		return -EINVAL;
25 	}
26 
27 	kfree(kern_buf);
28 	kfree(bnad->regdata);
29 	bnad->reglen = 0;
30 
31 	bnad->regdata = kzalloc(len << 2, GFP_KERNEL);
32 	if (!bnad->regdata)
33 		return -ENOMEM;
34 
35 	bnad->reglen = len << 2;
36 	rb = bfa_ioc_bar0(ioc);
37 	addr &= BFA_REG_ADDRMSK(ioc);
38 
39 	/* offset and len sanity check */
40 	rc = bna_reg_offset_check(ioc, addr, len);
41 	if (rc) {
42 		netdev_warn(bnad->netdev, "failed reg offset check\n");
43 		kfree(bnad->regdata);
44 		bnad->regdata = NULL;
45 		bnad->reglen = 0;
46 		return -EINVAL;
47 	}
48 
49 	reg_addr = rb + addr;
50 	regbuf =  (u32 *)bnad->regdata;
51 	spin_lock_irqsave(&bnad->bna_lock, flags);
52 	for (i = 0; i < len; i++) {
53 		*regbuf = readl(reg_addr);
54 		regbuf++;
55 		reg_addr += sizeof(u32);
56 	}
57 	spin_unlock_irqrestore(&bnad->bna_lock, flags);
58 
59 	return nbytes;
60 }
```
which has a vulnerability among CWE-125 and among lines:
```
16 	kern_buf = memdup_user(buf, nbytes);
```
Please generate five possible patches for the vulnerability.