Bluetooth: btrtl: Use kvmalloc for FW allocations

Currently, kmemdup is applied to the firmware data, and it invokes
kmalloc under the hood. The firmware size and patch_length are big (more
than PAGE_SIZE), and on some low-end systems (like ASUS E202SA) kmalloc
may fail to allocate a contiguous chunk under high memory usage and
fragmentation:

Bluetooth: hci0: RTL: examining hci_ver=06 hci_rev=000a lmp_ver=06 lmp_subver=8821
Bluetooth: hci0: RTL: rom_version status=0 version=1
Bluetooth: hci0: RTL: loading rtl_bt/rtl8821a_fw.bin
kworker/u9:2: page allocation failure: order:4, mode:0x40cc0(GFP_KERNEL|__GFP_COMP), nodemask=(null),cpuset=/,mems_allowed=0
<stack trace follows>

As firmware load happens on each resume, Bluetooth will stop working
after several iterations, when the kernel fails to allocate an order-4
page.

This patch replaces kmemdup with kvmalloc+memcpy. It's not required to
have a contiguous chunk here, because it's not mapped to the device
directly.
Signed-off-by: Maxim Mikityanskiy <maxtram95@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/btrtl.c

@@ -370,11 +370,11 @@ static int rtlbt_parse_firmware(struct hci_dev *hdev,
 	 * the end.
 	 */
 	len = patch_length;
-	buf = kmemdup(btrtl_dev->fw_data + patch_offset, patch_length,
-		      GFP_KERNEL);
+	buf = kvmalloc(patch_length, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
 
+	memcpy(buf, btrtl_dev->fw_data + patch_offset, patch_length - 4);
 	memcpy(buf + patch_length - 4, &epatch_info->fw_version, 4);
 
 	*_buf = buf;
@@ -460,8 +460,10 @@ static int rtl_load_file(struct hci_dev *hdev, const char *name, u8 **buff)
 	if (ret < 0)
 		return ret;
 	ret = fw->size;
-	*buff = kmemdup(fw->data, ret, GFP_KERNEL);
-	if (!*buff)
+	*buff = kvmalloc(fw->size, GFP_KERNEL);
+	if (*buff)
+		memcpy(*buff, fw->data, ret);
+	else
 		ret = -ENOMEM;
 
 	release_firmware(fw);
@@ -499,14 +501,14 @@ static int btrtl_setup_rtl8723b(struct hci_dev *hdev,
 		goto out;
 
 	if (btrtl_dev->cfg_len > 0) {
-		tbuff = kzalloc(ret + btrtl_dev->cfg_len, GFP_KERNEL);
+		tbuff = kvzalloc(ret + btrtl_dev->cfg_len, GFP_KERNEL);
 		if (!tbuff) {
 			ret = -ENOMEM;
 			goto out;
 		}
 
 		memcpy(tbuff, fw_data, ret);
-		kfree(fw_data);
+		kvfree(fw_data);
 
 		memcpy(tbuff + ret, btrtl_dev->cfg_data, btrtl_dev->cfg_len);
 		ret += btrtl_dev->cfg_len;
@@ -519,14 +521,14 @@ static int btrtl_setup_rtl8723b(struct hci_dev *hdev,
 	ret = rtl_download_firmware(hdev, fw_data, ret);
 
 out:
-	kfree(fw_data);
+	kvfree(fw_data);
 	return ret;
 }
 
 void btrtl_free(struct btrtl_device_info *btrtl_dev)
 {
-	kfree(btrtl_dev->fw_data);
-	kfree(btrtl_dev->cfg_data);
+	kvfree(btrtl_dev->fw_data);
+	kvfree(btrtl_dev->cfg_data);
 	kfree(btrtl_dev);
 }
 EXPORT_SYMBOL_GPL(btrtl_free);