On Tue, Jul 20, 2021 at 12:54:16PM -0700, Erdem Aktas wrote: > Now let's say the kernel wants to access a page for the first time, or > after a kexec it wants to make sure all the pages are private. it > needs to call tdx_hcall_gpa_intent or tdg_accept_page individually. > If the page is already accepted, tdg_accept_page does not return any > error in the current implementation in v3. Depending on how this page > is being used, it's content is now "not zeroed" as opposed to what it > is being expected. Converting this to an attack is not trivial but > possible. You mean when the TDVF is changed? In this case the unaccepted memory will be a different memory type, so not lazy accept enabled kernels wouldn't use it. > > I did not see any #VE implementation to handle SEPT violations when a > page is in PENDING state. I am assuming that this needs to be > supported at some point (If not then we need to discuss the use cases > for such support). We actually plan to disable those #VEs, to avoid any problems with the system call gap. Instead the plan is that the kernel will know in advance what memory has been accepted or not, and accept it before touching. -Andi
