Currently, all task switches check privileges against the DPL of the TSS. This is only correct for jmp/call to a TSS. If a task gate is used, the DPL of this take gate is used for the check instead. Exceptions, external interrupts and iret shouldn't perform any check.
Signed-off-by: Kevin Wolf <kw...@redhat.com> --- arch/x86/include/asm/kvm_emulate.h | 2 +- arch/x86/include/asm/kvm_host.h | 4 +- arch/x86/kvm/emulate.c | 53 +++++++++++++++++++++++++++++++----- arch/x86/kvm/svm.c | 5 +++- arch/x86/kvm/vmx.c | 8 +++-- arch/x86/kvm/x86.c | 6 ++-- 6 files changed, 61 insertions(+), 17 deletions(-) diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h index ab4092e..c8a9cf3 100644 --- a/arch/x86/include/asm/kvm_emulate.h +++ b/arch/x86/include/asm/kvm_emulate.h @@ -372,7 +372,7 @@ bool x86_page_table_writing_insn(struct x86_emulate_ctxt *ctxt); #define EMULATION_INTERCEPTED 2 int x86_emulate_insn(struct x86_emulate_ctxt *ctxt); int emulator_task_switch(struct x86_emulate_ctxt *ctxt, - u16 tss_selector, int reason, + u16 tss_selector, int idt_index, int reason, bool has_error_code, u32 error_code); int emulate_int_real(struct x86_emulate_ctxt *ctxt, int irq); #endif /* _ASM_X86_KVM_X86_EMULATE_H */ diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 52d6640..0533fc4 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -741,8 +741,8 @@ int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu); void kvm_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg); int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector, int seg); -int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason, - bool has_error_code, u32 error_code); +int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index, + int reason, bool has_error_code, u32 error_code); int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3); diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 05a562b..7097ca9 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1151,6 +1151,22 @@ static int pio_in_emulated(struct x86_emulate_ctxt *ctxt, return 1; } +static int read_interrupt_descriptor(struct x86_emulate_ctxt *ctxt, + u16 index, struct kvm_desc_struct *desc) +{ + struct kvm_desc_ptr dt; + ulong addr; + + ctxt->ops->get_idt(ctxt, &dt); + + if (dt.size < index * 8 + 7) + return emulate_gp(ctxt, index << 3 | 0x2); + + addr = dt.address + index * 8; + return ctxt->ops->read_std(ctxt, addr, desc, sizeof *desc, + &ctxt->exception); +} + static void get_descriptor_table_ptr(struct x86_emulate_ctxt *ctxt, u16 selector, struct desc_ptr *dt) { @@ -2350,7 +2366,7 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt, } static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt, - u16 tss_selector, int reason, + u16 tss_selector, int idt_index, int reason, bool has_error_code, u32 error_code) { struct x86_emulate_ops *ops = ctxt->ops; @@ -2372,12 +2388,35 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt, /* FIXME: check that next_tss_desc is tss */ - if (reason != TASK_SWITCH_IRET) { - if ((tss_selector & 3) > next_tss_desc.dpl || - ops->cpl(ctxt) > next_tss_desc.dpl) - return emulate_gp(ctxt, 0); + /* + * Check privileges. The three cases are task switch caused by... + * + * 1. jmp/call/int to task gate: Check against DPL of the task gate + * 2. Exception/IRQ/iret: No check is performed + * 3. jmp/call to TSS: Check agains DPL of the TSS + */ + if (reason == TASK_SWITCH_GATE) { + if (idt_index != -1) { + /* Software interrupts */ + struct kvm_desc_struct task_gate_desc; + int dpl; + + ret = read_interrupt_descriptor(ctxt, idt_index, + &task_gate_desc); + if (ret != X86EMUL_CONTINUE) + return ret; + + dpl = task_gate_desc.dpl; + if ((tss_selector & 3) > dpl || ops->cpl(ctxt) > dpl) + return emulate_gp(ctxt, (idt_index << 3) | 0x2); + } + } else if (reason != TASK_SWITCH_IRET) { + int dpl = next_tss_desc.dpl; + if ((tss_selector & 3) > dpl || ops->cpl(ctxt) > dpl) + return emulate_gp(ctxt, tss_selector); } + desc_limit = desc_limit_scaled(&next_tss_desc); if (!next_tss_desc.p || ((desc_limit < 0x67 && (next_tss_desc.type & 8)) || @@ -2430,7 +2469,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt, } int emulator_task_switch(struct x86_emulate_ctxt *ctxt, - u16 tss_selector, int reason, + u16 tss_selector, int idt_index, int reason, bool has_error_code, u32 error_code) { int rc; @@ -2438,7 +2477,7 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt, ctxt->_eip = ctxt->eip; ctxt->dst.type = OP_NONE; - rc = emulator_do_task_switch(ctxt, tss_selector, reason, + rc = emulator_do_task_switch(ctxt, tss_selector, idt_index, reason, has_error_code, error_code); if (rc == X86EMUL_CONTINUE) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 5fa553b..6a977c1 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -2730,7 +2730,10 @@ static int task_switch_interception(struct vcpu_svm *svm) (int_vec == OF_VECTOR || int_vec == BP_VECTOR))) skip_emulated_instruction(&svm->vcpu); - if (kvm_task_switch(&svm->vcpu, tss_selector, reason, + if (int_type != SVM_EXITINTINFO_TYPE_SOFT) + int_vec = -1; + + if (kvm_task_switch(&svm->vcpu, tss_selector, int_vec, reason, has_error_code, error_code) == EMULATE_FAIL) { svm->vcpu.run->exit_reason = KVM_EXIT_INTERNAL_ERROR; svm->vcpu.run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 906a7e8..a335170 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -4672,9 +4672,10 @@ static int handle_task_switch(struct kvm_vcpu *vcpu) bool has_error_code = false; u32 error_code = 0; u16 tss_selector; - int reason, type, idt_v; + int reason, type, idt_v, idt_index; idt_v = (vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK); + idt_index = (vmx->idt_vectoring_info & VECTORING_INFO_VECTOR_MASK); type = (vmx->idt_vectoring_info & VECTORING_INFO_TYPE_MASK); exit_qualification = vmcs_readl(EXIT_QUALIFICATION); @@ -4712,8 +4713,9 @@ static int handle_task_switch(struct kvm_vcpu *vcpu) type != INTR_TYPE_NMI_INTR)) skip_emulated_instruction(vcpu); - if (kvm_task_switch(vcpu, tss_selector, reason, - has_error_code, error_code) == EMULATE_FAIL) { + if (kvm_task_switch(vcpu, tss_selector, + type == INTR_TYPE_SOFT_INTR ? idt_index : -1, reason, + has_error_code, error_code) == EMULATE_FAIL) { vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; vcpu->run->internal.ndata = 0; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1171def..dc3e945 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5541,15 +5541,15 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu, return 0; } -int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason, - bool has_error_code, u32 error_code) +int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index, + int reason, bool has_error_code, u32 error_code) { struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt; int ret; init_emulate_ctxt(vcpu); - ret = emulator_task_switch(ctxt, tss_selector, reason, + ret = emulator_task_switch(ctxt, tss_selector, idt_index, reason, has_error_code, error_code); if (ret) -- 1.7.6.5 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html