Re: [PATCH 1/6] x86/sgx: Do not consider unsanitized pages an error

jarkko
2022-08-31T02:45:06Z

On Wed, Aug 31, 2022 at 02:35:53AM +0000, Huang, Kai wrote:
> On Wed, 2022-08-31 at 05:15 +0300, jarkko@kernel.org wrote:
> > On Wed, Aug 31, 2022 at 01:27:58AM +0000, Huang, Kai wrote:
> > > On Tue, 2022-08-30 at 15:54 -0700, Reinette Chatre wrote:
> > > > Hi Jarkko,
> > > >
> > > > On 8/29/2022 8:12 PM, Jarkko Sakkinen wrote:
> > > > > In sgx_init(), if misc_register() for the provision device fails, and
> > > > > neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be
> > > > > prematurely stopped.
> > > >
> > > > I do not think misc_register() is required to fail for the scenario to
> > > > be triggered (rather use "or" than "and"?). Perhaps just
> > > > "In sgx_init(), if a failure is encountered after ksgxd is started
> > > > (via sgx_page_reclaimer_init()) ...".
> > >
> > > IMHO "a failure" might be too vague. For instance, failure to sgx_drv_init()
> > > won't immediately result in ksgxd to stop prematurally. As long as KVM SGX can
> > > be initialized successfully, sgx_init() still returns 0.
> > >
> > > Btw I was thinking whether we should move sgx_page_reclaimer_init() to the end
> > > of sgx_init(), after we make sure at least one of the driver and the KVM SGX is
> > > initialized successfully. Then the code change in this patch won't be necessary
> > > if I understand correctly. AFAICT there's no good reason to start the ksgxd at
> > > early stage before we are sure either the driver or KVM SGX will work.
> >
> > I would focus fixing the existing flow rather than reinventing the flow.
> >
> > It can be made to work, and therefore it is IMHO correct action to take.
>
> From another perspective, the *existing flow* is the reason which causes this
> bug. A real fix is to fix the flow itself.

Any existing flow in part of the kernel can have a bug. That
does not mean that switching flow would be proper way to fix
a bug.

BR, Jarkko