From e5c98b0e6059b8a108ef78ec4448c91af1f8232b Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Fri, 6 Jan 2017 20:05:36 +0000 Subject: [PATCH] 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 Reviewed-by: Jan Beulich --- 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 4f29c3af93..ea0ce528f3 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; -- 2.30.2