Loading and Unloading Wireless Drivers
This guide explains the process to load and unload a wireless driver. If there are two or more devices using the same driver, can cause unexpected results while using them for Wireless Pentesting, therefor we are able to unload (blacklist) one of them.
Determine the driver with airmon-ng
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kali@kali:~$ sudo airmon-ng
PHY Interface Driver Chipset
phy0 wlan0 ath9k_htc Qualcomm Atheros Communications AR9271 802.11n
Listing system USB devices and shows detailed information for each device:
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kali@kali:~# sudo lsusb -vv
Bus 001 Device 002: ID 0cf3:9271 Qualcomm Atheros Communications AR9271 802.11n
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 255 Vendor Specific Class
bDeviceSubClass 255 Vendor Specific Subclass
bDeviceProtocol 255 Vendor Specific Protocol
bMaxPacketSize0 64
idVendor 0x0cf3 Qualcomm Atheros Communications
idProduct 0x9271 AR9271 802.11n
bcdDevice 1.08
iManufacturer 16 ATHEROS
iProduct 32 USB2.0 WLAN
iSerial 48 12345
bNumConfigurations 1
...
Determining dependencies, compatibility, and firmware requirements are displayed with the modinfo command and the name of the driver. Running modinfo for the driver displays the following output:
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kali@kali:~$ sudo modinfo ath9k_htc
filename: /lib/modules/4.16.0-kali2-amd64/kernel/drivers/net/wireless/ath/ath9k/ath9k_htc.ko
firmware: ath9k_htc/htc_9271-1.4.0.fw
firmware: ath9k_htc/htc_7010-1.4.0.fw
description: Atheros driver 802.11n HTC based wireless devices
license: Dual BSD/GPL
author: Atheros Communications
alias: usb:v0CF3p20FFd*dc*dsc*dp*ic*isc*ip*in*
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alias: usb:v0CF3p1006d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v0CF3p9271d*dc*dsc*dp*ic*isc*ip*in*
depends: mac80211,ath9k_hw,ath9k_common,ath,cfg80211,usbcore
retpoline: Y
intree: Y
name: ath9k_htc
vermagic: 4.16.0-kali2-amd64 SMP mod_unload modversions
parm: debug:Debugging mask (uint)
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parm: blink:Enable LED blink on activity (int)
lsmod lists all the loaded modules as well as the dependencies of each module. Running the command with the driver loaded outputs the following:
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kali@kali:~$ lsmod
Module Size Used by
ath9k_htc 81920 0
ath9k_common 20480 1 ath9k_htc
ath9k_hw 487424 2 ath9k_htc,ath9k_common
ath 32768 3 ath9k_htc,ath9k_hw,ath9k_common
mac80211 802816 1 ath9k_htc
cfg80211 737280 4 ath9k_htc,mac80211,ath,ath9k_common
rfkill 28672 3 cfg80211
uhci_hcd 49152 0
ehci_pci 16384 0
ehci_hcd 94208 1 ehci_pci
ata_piix 36864 0
mptscsih 36864 1 mptspi
usbcore 290816 5 ath9k_htc,usbhid,ehci_hcd,uhci_hcd,ehci_pci
usb_common 16384 1 usbcore
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A good example of when to use blacklisting would be the case where an open source driver and the closed source vendor drivers are both present on the system. If we run modinfo on both of them, we will see they share similar IDs. There should only be one driver claiming a device at a time, so we have to blacklist one of them. If we don’t, the two drivers will fight for the same resource, causing unexpected results.
lsmod lists all the loaded modules as well as the dependencies of each module. Running the command with the ath9k_htc driver loaded outputs the following:
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kali@kali:~$ lsmod
Module Size Used by
ath9k_htc 81920 0
ath9k_common 20480 1 ath9k_htc
ath9k_hw 487424 2 ath9k_htc,ath9k_common
ath 32768 3 ath9k_htc,ath9k_hw,ath9k_common
mac80211 802816 1 ath9k_htc
cfg80211 737280 4 ath9k_htc,mac80211,ath,ath9k_common
rfkill 28672 3 cfg80211
uhci_hcd 49152 0
ehci_pci 16384 0
ehci_hcd 94208 1 ehci_pci
ata_piix 36864 0
mptscsih 36864 1 mptspi
usbcore 290816 5 ath9k_htc,usbhid,ehci_hcd,uhci_hcd,ehci_pci
usb_common 16384 1 usbcore
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With our lsmod output, we can start removing modules that are not needed by other drivers. If we are unsure which module to remove next, we can run lsmod again and find one that isn’t used by any other.
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kali@kali:~$ sudo rmmod ath9k_htc ath9k_common ath9k_hw ath