On Mon, Mar 14, 2022 at 04:49:37AM +0200, Jarkko Sakkinen wrote: > On Fri, Mar 11, 2022 at 09:53:29AM -0800, Reinette Chatre wrote: > > > I saw Haitao's note that EMODPE requires "Read access permitted by enclave". > > This motivates that EMODPR->PROT_NONE should not be allowed since it would > > not be possible to relax permissions (run EMODPE) after that. Even so, I > > also found in the SDM that EACCEPT has the note "Read access permitted > > by enclave". That seems to indicate that EMODPR->PROT_NONE is not practical > > from that perspective either since the enclave will not be able to > > EACCEPT the change. Does that match your understanding? > > Yes, PROT_NONE should not be allowed. > > This is however the real problem. > > The current kernel patch set has inconsistent API and EMODPR ioctl is > simply unacceptable. It also requires more concurrency management from > user space run-time, which would be heck a lot easier to do in the kernel. > > If you really want EMODPR as ioctl, then for consistencys sake, then EAUG > should be too. Like this when things go opposite directions, this patch set > plain and simply will not work out. > > I would pick EAUG's strategy from these two as it requires half the back > calls to host from an enclave. I.e. please combine mprotect() and EMODPR, > either in the #PF handler or as part of mprotect(), which ever suits you > best. > > I'll try demonstrate this with two examples. > > mmap() could go something like this() (simplified): > 1. Execution #UD's to SYSCALL. > 2. Host calls enclave's mmap() handler with mmap() parameters. > 3. Enclave up-calls host's mmap(). > 4. Loops the range with EACCEPTCOPY. > > mprotect() has to be done like this: > 1. Execution #UD's to SYSCALL. > 2. Host calls enclave's mprotect() handler. > 3. Enclave up-calls host's mprotect(). > 4. Enclave up-calls host's ioctl() to SGX_IOC_ENCLAVE_PERMISSIONS. > 3. Loops the range with EACCEPT. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5. Loops the range with EACCEPT + EMODPE. > This is just terrible IMHO. I hope these examples bring some insight. BR, Jarkko
