Re: [PATCH v2 5/8] x86/iommu: the code addressing CVE-2011-1898 is VT-d specific

[Xenia Ragiadakou <burzalodowa@xxxxxxxxx>]

On 1/12/23 14:01, Jan Beulich wrote:
> On 04.01.2023 09:44, Xenia Ragiadakou wrote:
> > The variable untrusted_msi indicates whether the system is vulnerable to
> > CVE-2011-1898. This vulnerablity is VT-d specific.
> As per the reply by Andrew to v1, this vulnerability is generic to intremap-
> incapable or intremap-disabled configurations. You want to say so. In turn
> I wonder whether instead of the changes you're making you wouldn't want to
> move the definition of the variable to xen/drivers/passthrough/x86/iommu.c.
> A useful further step might be to guard its definition (not necessarily
> its declaration; see replies to earlier patches) by CONFIG_PV instead (of
> course I understand that's largely orthogonal to your series here, yet it
> would fit easily with moving the definition).
Sure I can do that.

> > --- a/xen/arch/x86/include/asm/iommu.h
> > +++ b/xen/arch/x86/include/asm/iommu.h
> > @@ -127,7 +127,9 @@ int iommu_identity_mapping(struct domain *d, p2m_access_t 
> > p2ma,
> >                              unsigned int flag);
> >   void iommu_identity_map_teardown(struct domain *d);
> >   
> > +#ifdef CONFIG_INTEL_IOMMU
> >   extern bool untrusted_msi;
> > +#endif
> As per above / earlier comments I don't think this part is needed in any
> event.
>
> > --- a/xen/arch/x86/pv/hypercall.c
> > +++ b/xen/arch/x86/pv/hypercall.c
> > @@ -193,8 +193,10 @@ void pv_ring1_init_hypercall_page(void *p)
> >   
> >   void do_entry_int82(struct cpu_user_regs *regs)
> >   {
> > +#ifdef CONFIG_INTEL_IOMMU
> >       if ( unlikely(untrusted_msi) )
> >           check_for_unexpected_msi((uint8_t)regs->entry_vector);
> > +#endif
> >   
> >       _pv_hypercall(regs, true /* compat */);
> >   }
> > diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
> > index ae01285181..8f2fb36770 100644
> > --- a/xen/arch/x86/x86_64/entry.S
> > +++ b/xen/arch/x86/x86_64/entry.S
> > @@ -406,11 +406,13 @@ ENTRY(int80_direct_trap)
> >   .Lint80_cr3_okay:
> >           sti
> >   
> > +#ifdef CONFIG_INTEL_IOMMU
> >           cmpb  $0,untrusted_msi(%rip)
> >   UNLIKELY_START(ne, msi_check)
> >           movl  $0x80,%edi
> >           call  check_for_unexpected_msi
> >   UNLIKELY_END(msi_check)
> > +#endif
> >   
> >           movq  STACK_CPUINFO_FIELD(current_vcpu)(%rbx), %rbx
> >   
--
Xenia