CVE-2021-46980

In the Linux kernel, the following vulnerability has been resolved: usb:
typec: ucsi: Retrieve all the PDOs instead of just the first 4 commit
4dbc6a4ef06d (“usb: typec: ucsi: save power data objects in PD mode”)
introduced retrieval of the PDOs when connected to a PD-capable source. But
only the first 4 PDOs are received since that is the maximum number that
can be fetched at a time given the MESSAGE_IN length limitation (16 bytes).
However, as per the PD spec a connected source may advertise up to a
maximum of 7 PDOs. If such a source is connected it’s possible the PPM
could have negotiated a power contract with one of the PDOs at index
greater than 4, and would be reflected in the request data object’s (RDO)
object position field. This would result in an out-of-bounds access when
the rdo_index() is used to index into the src_pdos array in
ucsi_psy_get_voltage_now(). With the help of the UBSAN
-fsanitize=array-bounds checker enabled this exact issue is revealed when
connecting to a PD source adapter that advertise 5 PDOs and the PPM enters
a contract having selected the 5th one. [ 151.545106][ T70] Unexpected
kernel BRK exception at EL1 [ 151.545112][ T70] Internal error: BRK
handler: f2005512 [#1] PREEMPT SMP … [ 151.545499][ T70] pc :
ucsi_psy_get_prop+0x208/0x20c [ 151.545507][ T70] lr :
power_supply_show_property+0xc0/0x328 … [ 151.545542][ T70] Call trace: [
151.545544][ T70] ucsi_psy_get_prop+0x208/0x20c [ 151.545546][ T70]
power_supply_uevent+0x1a4/0x2f0 [ 151.545550][ T70] dev_uevent+0x200/0x384
[ 151.545555][ T70] kobject_uevent_env+0x1d4/0x7e8 [ 151.545557][ T70]
power_supply_changed_work+0x174/0x31c [ 151.545562][ T70]
process_one_work+0x244/0x6f0 [ 151.545564][ T70] worker_thread+0x3e0/0xa64
We can resolve this by instead retrieving and storing up to the maximum of
7 PDOs in the con->src_pdos array. This would involve two calls to the
GET_PDOS command.