[Xen-changelog] [xen master] x86/pv: Check that emulate_privileged_op() don't change any unexpected flags

[patchbot@xxxxxxx]

commit e5c98b0e6059b8a108ef78ec4448c91af1f8232b
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Jan 6 20:05:36 2017 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Mon Jan 16 17:37:26 2017 +0000

    x86/pv: Check that emulate_privileged_op() don't change any unexpected flags
    
    No bits, other than arithmetic ones and the resume flag (which will most
    likely change from 1 to 0), can be changed by the instructions we permit.
    Extend the check to cover other flags.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/traps.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 4f29c3a..ea0ce52 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -3012,9 +3012,11 @@ static int emulate_privileged_op(struct cpu_user_regs 
*regs)
 
     /*
      * Un-mirror virtualized state from EFLAGS.
-     * Nothing we allow to be emulated can change TF, IF, or IOPL.
+     * Nothing we allow to be emulated can change anything other than the
+     * arithmetic bits, and the resume flag.
      */
-    ASSERT(!((regs->_eflags ^ eflags) & (X86_EFLAGS_IF | X86_EFLAGS_IOPL)));
+    ASSERT(!((regs->_eflags ^ eflags) &
+             ~(X86_EFLAGS_RF | X86_EFLAGS_ARITH_MASK)));
     regs->_eflags |= X86_EFLAGS_IF;
     regs->_eflags &= ~X86_EFLAGS_IOPL;
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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