[Xen-changelog] [xen staging] x86/hvm: add nospec to hvmop param

[patchbot@xxxxxxx]

commit 93dfd72bdb43b35dbb1424c476d17aac67e82837
Author:     Norbert Manthey <nmanthey@xxxxxxxxx>
AuthorDate: Thu Mar 14 13:56:00 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Apr 5 12:18:34 2019 +0200

    x86/hvm: add nospec to hvmop param
    
    The params array in hvm can be accessed with get and set functions.
    As the index is guest controlled, make sure no out-of-bound accesses
    can be performed.
    
    As we cannot influence how future compilers might modify the
    instructions that enforce the bounds, we furthermore block speculation,
    so that the update is visible in the architectural state.
    
    This is part of the speculative hardening effort.
    
    Signed-off-by: Norbert Manthey <nmanthey@xxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 11ce21fc08..e798b49b66 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4145,6 +4145,9 @@ static int hvmop_set_param(
     if ( a.index >= HVM_NR_PARAMS )
         return -EINVAL;
 
+    /* Make sure the above bound check is not bypassed during speculation. */
+    block_speculation();
+
     d = rcu_lock_domain_by_any_id(a.domid);
     if ( d == NULL )
         return -ESRCH;
@@ -4411,6 +4414,9 @@ static int hvmop_get_param(
     if ( a.index >= HVM_NR_PARAMS )
         return -EINVAL;
 
+    /* Make sure the above bound check is not bypassed during speculation. */
+    block_speculation();
+
     d = rcu_lock_domain_by_any_id(a.domid);
     if ( d == NULL )
         return -ESRCH;
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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