Re: [edk2-devel] static data in dxe_runtime modules

["Laszlo Ersek" <lersek@redhat.com>]

On 08/12/19 20:43, Roman Kagan wrote:
> On Fri, Aug 09, 2019 at 04:07:00PM +0000, Roman Kagan via Groups.Io wrote:
>> On Thu, Aug 08, 2019 at 07:39:14PM +0200, Laszlo Ersek wrote:
>>> On 08/07/19 19:41, Andrew Fish wrote:
>>>>> On Aug 7, 2019, at 10:29 AM, Laszlo Ersek <lersek@redhat.com> wrote:
>>>>> On 08/05/19 12:18, Roman Kagan wrote:
>>>>>> On Sat, Aug 03, 2019 at 04:03:04AM +0200, Laszlo Ersek via Groups.Io wrote:
>>>>>>> On 08/01/19 21:16, Roman Kagan wrote:
>>>>> I'm convinced that OpenSSL needs to expose a new API for this particular
>>>>> problem.
>>
>> Since, as you point out below, the problem only affects the essentially
>> broken configuration (SECURE_BOOT_ENABLE && !SMM_REQUIRE), I'm fine with
>> saving time and effort and sticking to the hack-ish approach proposed in
>> the bugzilla issue, which is to iterate over "thread-local" pointers and
>> EfiConvertPointer() on each.  (As long as it fixes the problem of
>> course; I'll test and report back.)
> 
> It doesn't :(  It just gets slightly further and hits another static
> pointer variable which is not part of the thread-local array:
> 
> ...
>   Pkcs7Verify
>     EVP_add_digest
>       OBJ_NAME_add
> 
> this one uses a few static pointer variables that are also initialized
> on demand and become stale upon SetVirtualAddressMap().

So it looks like the issue can't be solved without making OpenSSL aware
of this use case.

>> So we should be good without a new API from OpenSSL.
> 
>>> In other words, the problem doesn't exist when OpenSSL (with the rest of
>>> the variable driver stack) is protected with SMM, as pointers into SMRAM
>>> remain valid "forever", after the initial SMM driver dispatch.
>>
>> Makes perfect sense.  We happen to build this broken configuration for
>> some historical reasons, I'm failing to recall exactly which.  Will try
>> to get rid of it.
> 
> We appear to have some i440fx-based VMs with SecureBoot in the field
> (dunno about their origin) and those don't allow SMM.

Indeed i440fx has no support for SMM/SMRAM -- but that only means that
Secure Boot cannot be made actually secure on i440fx.

Red Hat used to offer an OVMF binary that ran on i440fx too, and
included the Secure Boot feature without SMM. But the package containing
that binary was always marked as Tech Preview. When we exited Tech
Preview with OVMF, we removed said binary.

Thanks
Laszlo