[Xen-changelog] [xen staging] x86/CPUID: block speculative out-of-bound accesses

[patchbot@xxxxxxx]

commit fd2f602c2f85944beb715559136f752a282b3836
Author:     Norbert Manthey <nmanthey@xxxxxxxxx>
AuthorDate: Mon Jan 28 17:38:29 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Jan 28 17:38:29 2019 +0100

    x86/CPUID: block speculative out-of-bound accesses
    
    During instruction emulation, the cpuid instruction is emulated with
    data that is controlled by the guest. As speculation might pass bound
    checks, we have to ensure that no out-of-bound loads are possible.
    
    To not rely on the compiler to perform value propagation, instead of
    using the array_index_nospec macro, we replace the variable with the
    constant to be propagated instead.
    
    This commit is part of the SpectreV1+L1TF mitigation patch series.
    
    Signed-off-by: Norbert Manthey <nmanthey@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/cpuid.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index 0591a7dc60..ab0aab678c 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -1,6 +1,7 @@
 #include <xen/init.h>
 #include <xen/lib.h>
 #include <xen/sched.h>
+#include <xen/nospec.h>
 #include <asm/cpuid.h>
 #include <asm/hvm/hvm.h>
 #include <asm/hvm/nestedhvm.h>
@@ -629,7 +630,7 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
             if ( subleaf >= ARRAY_SIZE(p->cache.raw) )
                 return;
 
-            *res = p->cache.raw[subleaf];
+            *res = array_access_nospec(p->cache.raw, subleaf);
             break;
 
         case 0x7:
@@ -638,25 +639,25 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
                                  ARRAY_SIZE(p->feat.raw) - 1) )
                 return;
 
-            *res = p->feat.raw[subleaf];
+            *res = array_access_nospec(p->feat.raw, subleaf);
             break;
 
         case 0xb:
             if ( subleaf >= ARRAY_SIZE(p->topo.raw) )
                 return;
 
-            *res = p->topo.raw[subleaf];
+            *res = array_access_nospec(p->topo.raw, subleaf);
             break;
 
         case XSTATE_CPUID:
             if ( !p->basic.xsave || subleaf >= ARRAY_SIZE(p->xstate.raw) )
                 return;
 
-            *res = p->xstate.raw[subleaf];
+            *res = array_access_nospec(p->xstate.raw, subleaf);
             break;
 
         default:
-            *res = p->basic.raw[leaf];
+            *res = array_access_nospec(p->basic.raw, leaf);
             break;
         }
         break;
@@ -680,7 +681,7 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
                                      ARRAY_SIZE(p->extd.raw) - 1) )
             return;
 
-        *res = p->extd.raw[leaf & 0xffff];
+        *res = array_access_nospec(p->extd.raw, leaf & 0xffff);
         break;
 
     default:
@@ -847,7 +848,7 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
         if ( is_pv_domain(d) && is_hardware_domain(d) &&
              guest_kernel_mode(v, regs) && cpu_has_monitor &&
              regs->entry_vector == TRAP_gp_fault )
-            *res = raw_cpuid_policy.basic.raw[leaf];
+            *res = raw_cpuid_policy.basic.raw[5];
         break;
 
     case 0x7:
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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