CVE-2021-46980

/// Technical description

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

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References