[v2,2/2] x86: validate VM assist value in arch_set_info_guest()

Commit Message

Jan Beulich April 14, 2020, 11:35 a.m. UTC

While I can't spot anything that would go wrong, just like the
respective hypercall only permits applicable bits to be set, we should
also do so when loading guest context.

Reported-by: Andrew Cooper <[e-mail]>
Signed-off-by: Jan Beulich <[e-mail]>
---
I'd like to note that Arm lacks a field to save/restore vm_assist.

Comments

Andrew Cooper April 20, 2020, 8:16 p.m. UTC | #1

On 14/04/2020 12:35, Jan Beulich wrote:
> While I can't spot anything that would go wrong, just like the
> respective hypercall only permits applicable bits to be set, we should
> also do so when loading guest context.
>
> Reported-by: Andrew Cooper <[e-mail]>
> Signed-off-by: Jan Beulich <[e-mail]>

Acked-by: Andrew Cooper <[e-mail]>

Patch

--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -932,6 +932,9 @@  int arch_set_info_guest(
         }
     }
 
+    if ( v->vcpu_id == 0 && (c(vm_assist) & ~arch_vm_assist_valid(d)) )
+        return -EINVAL;
+
     if ( is_hvm_domain(d) )
     {
         for ( i = 0; i < ARRAY_SIZE(v->arch.dr); ++i )