misc: eeprom/idt_89hpesx: Switch to memdup_user_nul() helper

Use memdup_user_nul() helper instead of open-coding to simplify the code.

Signed-off-by: Ruan Jinjie <[e-mail]>
Reviewed-by: Luca Ceresoli <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/eeprom/idt_89hpesx.c

···
 		return 0;
 
 	/* Copy data from User-space */
-	buf = kmalloc(count + 1, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	if (copy_from_user(buf, ubuf, count)) {
-		ret = -EFAULT;
-		goto free_buf;
-	}
-	buf[count] = 0;
+	buf = memdup_user_nul(ubuf, count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
 
 	/* Find position of colon in the buffer */
 	colon_ch = strnchr(buf, count, ':');