[Xen-devel] [PATCH SpectreV1+L1TF v5 6/9] is_control_domain: block speculation

[Norbert Manthey <nmanthey@xxxxxxxxx>]

Checks of domain properties, such as is_hardware_domain or is_hvm_domain,
might be bypassed by speculatively executing these instructions. A reason
for bypassing these checks is that these macros access the domain
structure via a pointer, and check a certain field. Since this memory
access is slow, the CPU assumes a returned value and continues the
execution.

In case an is_control_domain check is bypassed, for example during a
hypercall, data that should only be accessible by the control domain could
be loaded into the cache.

Signed-off-by: Norbert Manthey <nmanthey@xxxxxxxxx>

---
 xen/include/xen/sched.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -23,6 +23,7 @@
 #include <asm/atomic.h>
 #include <xen/vpci.h>
 #include <xen/wait.h>
+#include <xen/nospec.h>
 #include <public/xen.h>
 #include <public/domctl.h>
 #include <public/sysctl.h>
@@ -908,10 +909,10 @@ void watchdog_domain_destroy(struct domain *d);
  *    (that is, this would not be suitable for a driver domain)
  *  - There is never a reason to deny the hardware domain access to this
  */
-#define is_hardware_domain(_d) ((_d) == hardware_domain)
+#define is_hardware_domain(_d) evaluate_nospec((_d) == hardware_domain)
 
 /* This check is for functionality specific to a control domain */
-#define is_control_domain(_d) ((_d)->is_privileged)
+#define is_control_domain(_d) evaluate_nospec((_d)->is_privileged)
 
 #define VM_ASSIST(d, t) (test_bit(VMASST_TYPE_ ## t, &(d)->vm_assist))
 
-- 
2.7.4




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