On Sat, Jul 04, 2020 at 04:43:49AM +0300, Jarkko Sakkinen wrote:

On Mon, Jun 29, 2020 at 08:27:19AM -0700, Sean Christopherson wrote:

quoted

On Sat, Jun 27, 2020 at 07:43:35PM +0200, Borislav Petkov wrote:

quoted

And you could do similar sanity checks in the other ioctl functions.

Ya, as above, SGX_ENCL_INITIALIZED can be checked here.

SGX_ENCL_DEAD is actually already checked in in the top level sgx_ioctl(),
i.e. the check in sgx_encl_add_page() can technically be flat out dropped.

I say "technically" because I'm a bit torn over SGX_ENCL_DEAD; encl->lock
must be held to SGX_ENCL_DEAD (the page fault and reclaim flows rely on
this), but as it stands today only ioctl() paths (guarded by SGX_ENCL_IOCTL)
and sgx_release() (makes the ioctls() unreachable) set SGX_ENCL_DEAD.

So it's safe to check SGX_ENCL_DEAD from ioctl() context without holding
encl->lock, at least in the current code base, but it feels weird/sketchy.

In the end I don't think I have a strong opinion.  Removing the technically
unnecessary DEAD check in sgx_encl_add_page() is the simplest change, so it
may make sense to do that and nothing more for initial upstreaming.  Long
term, I fully expect we'll add paths that set SGX_ENCL_DEAD outside of
ioctl() context, e.g. to handle EPC OOM, but it wouldn't be a bad thing to
have a standalone commit in a future series to add DEAD checks (under
encl->lock) in the ADD and INIT flows.

AFAIK nonne of th ioctl's should not need SGX_ENCL_DEAD check.

I can't tell if the double negative was intended, but I took a peek at your
current master and see that you removed the SGX_ENCL_DEAD check in
sgx_ioctl().  That check needs to stay, e.g. if EEXTEND fails we absolutely
need to prevent any further operations on the enclave.

The above was calling out that additional checks on SGX_ENCL_DEAD after
acquiring encl->lock are not necessary because SGX_ENCL_DEAD can only be
set when the ioctls() are no longer reachable or from within an ioctl(),
which provides exclusivity via SGX_ENCL_IOCTL.