In the Linux kernel, the following vulnerability has been resolved:
usb: typec: tcpm: recover after failure to start the frs ams
Reset the port if the tcpm fails to start the FAST_ROLE_SWAP AMS by
initiating error recovery on it.
This helps in cases where some cables (incorrectly) signal an FRS to
an FRS capable port during disconnection. The TCPC autonomously starts
sourcing VBUS on detecting the FRS signal. However, the VBUS sourcing is
left on when the FAST_ROLE_SWAP AMS fails to start (as tcpm_sink_tx_ok
is 0 as CC is open due to the cable disconnect). This is because the
code sets the state to INVALID_STATE without resetting the port state.
Log snippet before changes:
[ 101.401960] AMS FAST_ROLE_SWAP start
[ 101.401971] Sink TX No Go
[ 101.401982] sourcing vbus
[ 101.401987] VBUS on
[ 101.402159] VBUS on
[ 109.257809] CC1: 0 -> 0, CC2: 5 -> 0 [state SNK_READY, polarity 1, disconnected]
[ 111.267442] VBUS on
After changes:
[ 70.541211] AMS FAST_ROLE_SWAP start
[ 70.541220] Sink TX No Go
[ 70.541228] state change SNK_READY -> ERROR_RECOVERY [rev3 NONE_AMS]
[ 70.541362] VBUS on
[ 70.541365] sourcing vbus
[ 70.541367] VBUS on
[ 70.541374] state change ERROR_RECOVERY -> PORT_RESET [rev3 NONE_AMS]
[ 70.541410] disable vbus discharge ret:0
[ 70.543028] Setting usb_comm capable false
[ 70.544009] Setting voltage/current limit 0 mV 0 mA
[ 70.544034] polarity 0
[ 70.544239] Requesting mux state 0, usb-role 0, orientation 0
[ 70.555550] cc:=0
[ 70.555595] pending state change PORT_RESET -> PORT_RESET_WAIT_OFF @ 100 ms [rev3 NONE_AMS]
[ 70.555697] VBUS off
[ 70.555702] VBUS VSAFE0V
[ 70.555762] CC1: 5 -> 0, CC2: 0 -> 0 [state PORT_RESET, polarity 0, disconnected]
[ 70.587794] VBUS off
[ 70.587799] VBUS VSAFE0V
[ 70.655672] state change PORT_RESET -> PORT_RESET_WAIT_OFF [delayed 100 ms]
[ 70.655682] state change PORT_RESET_WAIT_OFF -> SNK_UNATTACHED [rev3 NONE_AMS]
[ 70.655686] Start toggling
[ 70.656274] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]