tcg_pp_s4_issue.md

21. TCG PP S4 issue

Description:

TCG physical presence will record TCG PP flag (if user confirmation is required) to a variable (TCG2_PHYSICAL_PRESENCE_FLAGS_VARIABLE/gEfiTcg2PhysicalPresenceGuid). This variable is locked by EDKII_VARIABLE_LOCK_PROTOCOL.
In S4 resume path, the code Tcg2PhysicalPresenceLibProcessRequest finds it is S4 resume and return immediately. It does not call EDKII_VARIABLE_LOCK_PROTOCOL to lock the variable (TCG2_PHYSICAL_PRESENCE_FLAGS_VARIABLE/ gEfiTcg2PhysicalPresenceGuid).

Recommendation:

We need update Tcg2PhysicalPresenceLibProcessRequest to move S4 check AFTER variable lock.
This is addressed by EDK2 GIT 7b9b576c71c71ed134f50497fd58f862109dd80b.

Acknowledgments:

Reported by Coleman, Rusty [email protected].

References:

• USRT M1615