From 37f66bbef0920429b8cb5eddba849ec4308a9f8e Mon Sep 17 00:00:00 2001 From: Maxim Levitsky Date: Thu, 27 Aug 2020 20:11:44 +0300 Subject: KVM: emulator: more strict rsm checks. Don't ignore return values in rsm_load_state_64/32 to avoid loading invalid state from SMM state area if it was tampered with by the guest. This is primarly intended to avoid letting guest set bits in EFER (like EFER.SVME when nesting is disabled) by manipulating SMM save area. Signed-off-by: Maxim Levitsky Message-Id: <20200827171145.374620-8-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) (limited to 'arch') diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index d0e2825ae617..1d450d7710d6 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2505,9 +2505,14 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt, *reg_write(ctxt, i) = GET_SMSTATE(u32, smstate, 0x7fd0 + i * 4); val = GET_SMSTATE(u32, smstate, 0x7fcc); - ctxt->ops->set_dr(ctxt, 6, (val & DR6_VOLATILE) | DR6_FIXED_1); + + if (ctxt->ops->set_dr(ctxt, 6, (val & DR6_VOLATILE) | DR6_FIXED_1)) + return X86EMUL_UNHANDLEABLE; + val = GET_SMSTATE(u32, smstate, 0x7fc8); - ctxt->ops->set_dr(ctxt, 7, (val & DR7_VOLATILE) | DR7_FIXED_1); + + if (ctxt->ops->set_dr(ctxt, 7, (val & DR7_VOLATILE) | DR7_FIXED_1)) + return X86EMUL_UNHANDLEABLE; selector = GET_SMSTATE(u32, smstate, 0x7fc4); set_desc_base(&desc, GET_SMSTATE(u32, smstate, 0x7f64)); @@ -2560,16 +2565,23 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt, ctxt->eflags = GET_SMSTATE(u32, smstate, 0x7f70) | X86_EFLAGS_FIXED; val = GET_SMSTATE(u32, smstate, 0x7f68); - ctxt->ops->set_dr(ctxt, 6, (val & DR6_VOLATILE) | DR6_FIXED_1); + + if (ctxt->ops->set_dr(ctxt, 6, (val & DR6_VOLATILE) | DR6_FIXED_1)) + return X86EMUL_UNHANDLEABLE; + val = GET_SMSTATE(u32, smstate, 0x7f60); - ctxt->ops->set_dr(ctxt, 7, (val & DR7_VOLATILE) | DR7_FIXED_1); + + if (ctxt->ops->set_dr(ctxt, 7, (val & DR7_VOLATILE) | DR7_FIXED_1)) + return X86EMUL_UNHANDLEABLE; cr0 = GET_SMSTATE(u64, smstate, 0x7f58); cr3 = GET_SMSTATE(u64, smstate, 0x7f50); cr4 = GET_SMSTATE(u64, smstate, 0x7f48); ctxt->ops->set_smbase(ctxt, GET_SMSTATE(u32, smstate, 0x7f00)); val = GET_SMSTATE(u64, smstate, 0x7ed0); - ctxt->ops->set_msr(ctxt, MSR_EFER, val & ~EFER_LMA); + + if (ctxt->ops->set_msr(ctxt, MSR_EFER, val & ~EFER_LMA)) + return X86EMUL_UNHANDLEABLE; selector = GET_SMSTATE(u32, smstate, 0x7e90); rsm_set_desc_flags(&desc, GET_SMSTATE(u32, smstate, 0x7e92) << 8); -- cgit v1.2.3-59-g8ed1b