On Thu, Oct 10, 2019 at 10:09:21AM -0700, Sean Christopherson wrote: > On Thu, Oct 10, 2019 at 04:37:53PM +0300, Jarkko Sakkinen wrote: > > On Thu, Oct 10, 2019 at 02:37:45PM +0300, Jarkko Sakkinen wrote: > > > tag v23-rc2 > > > Tagger: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> > > > Date: Thu Oct 10 14:33:07 2019 +0300 > > > > > > x86/sgx: v23-rc1 patch set > > > > > > * Return -EIO instead of -ECANCELED when ptrace() fails to read a TCS page. > > > * In the reclaimer, pin page before ENCLS[EBLOCK] because pinning can fail > > > (because of OOM) even in legit behaviour and after EBLOCK the reclaiming > > > flow can be only reverted by killing the whole enclave. > > > * Fixed SGX_ATTR_RESERVED_MASK. Bit 7 was marked as reserved while in fact > > > it should have been bit 6 (Table 37-3 in the SDM). > > > * Return -EPERM from SGX_IOC_ENCLAVE_INIT when ENCLS[EINIT] returns an SGX > > > error code. > > > * In v22 __uaccess_begin() was used to pin the source page in > > > __sgx_encl_add_page(). Switch to get_user_pages() in order to avoid > > > deadlock (mmap_sem might get locked twice in the same thread). > > > > __uaccess_begin() is also needed to performan access checks the legit > > __uaccess_begin() doesn't check the address space, it temporarily disables > SMAP/SMEP so that the kernel can access a user mapping. An explicit > access_ok() call should be added as well. > > > user space address. What we can do is to use get_user_pages() just to > > make sure that the page is faulted while we perform ENCLS[EADD]. > > > > I updated the master branch with the fix for this. Now the access > > pattern is: > > > > ret = get_user_pages(src, 1, 0, &src_page, NULL); > > if (ret < 1) > > return ret; > > > > __uaccess_begin(); > > This should be immediately before __eadd(). I also think it'd be a good > idea to disable page faults around __eadd() so that an unexpected #PF > manifests as an __eadd() failure and not a kernel hang. Scratch that, using the userspace is address is flat out wrong. gup() doesn't guarantee the userspace mapping is valid, i.e. EADD can still get a #PF and deadlock. AIUI, the correct/bulletproof approach is to kmap() after gup() and use the kernel translation.
