diff options
| -rw-r--r-- | arch/x86/kvm/emulate.c | 35 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 9 |
2 files changed, 44 insertions, 0 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 48b067b179e0..59f93f68718a 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1554,6 +1554,37 @@ static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt, return linear_write_system(ctxt, addr, desc, sizeof(*desc)); } +static bool emulator_is_ssp_invalid(struct x86_emulate_ctxt *ctxt, u8 cpl) +{ + const u32 MSR_IA32_X_CET = cpl == 3 ? MSR_IA32_U_CET : MSR_IA32_S_CET; + u64 efer = 0, cet = 0, ssp = 0; + + if (!(ctxt->ops->get_cr(ctxt, 4) & X86_CR4_CET)) + return false; + + if (ctxt->ops->get_msr(ctxt, MSR_EFER, &efer)) + return true; + + /* SSP is guaranteed to be valid if the vCPU was already in 32-bit mode. */ + if (!(efer & EFER_LMA)) + return false; + + if (ctxt->ops->get_msr(ctxt, MSR_IA32_X_CET, &cet)) + return true; + + if (!(cet & CET_SHSTK_EN)) + return false; + + if (ctxt->ops->get_msr(ctxt, MSR_KVM_INTERNAL_GUEST_SSP, &ssp)) + return true; + + /* + * On transfer from 64-bit mode to compatibility mode, SSP[63:32] must + * be 0, i.e. SSP must be a 32-bit value outside of 64-bit mode. + */ + return ssp >> 32; +} + static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, u16 selector, int seg, u8 cpl, enum x86_transfer_type transfer, @@ -1694,6 +1725,10 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, if (efer & EFER_LMA) goto exception; } + if (!seg_desc.l && emulator_is_ssp_invalid(ctxt, cpl)) { + err_code = 0; + goto exception; + } /* CS(RPL) <- CPL */ selector = (selector & 0xfffc) | cpl; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 31aaff9db083..0a4e58dddf36 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8741,6 +8741,15 @@ static int emulator_set_msr_with_filter(struct x86_emulate_ctxt *ctxt, static int emulator_get_msr(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 *pdata) { + /* + * Treat emulator accesses to the current shadow stack pointer as host- + * initiated, as they aren't true MSR accesses (SSP is a "just a reg"), + * and this API is used only for implicit accesses, i.e. not RDMSR, and + * so the index is fully KVM-controlled. + */ + if (unlikely(msr_index == MSR_KVM_INTERNAL_GUEST_SSP)) + return kvm_msr_read(emul_to_vcpu(ctxt), msr_index, pdata); + return __kvm_emulate_msr_read(emul_to_vcpu(ctxt), msr_index, pdata); } |