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Commit f850e2e6 authored by Gleb Natapov's avatar Gleb Natapov Committed by Marcelo Tosatti
Browse files

KVM: x86 emulator: Check IOPL level during io instruction emulation 



Make emulator check that vcpu is allowed to execute IN, INS, OUT,
OUTS, CLI, STI.

Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Cc: stable@kernel.org
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 1871c602

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -678,6 +678,7 @@ void kvm_disable_tdp(void); 


int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3);

int complete_pio(struct kvm_vcpu *vcpu);

bool kvm_check_iopl(struct kvm_vcpu *vcpu);



struct kvm_memory_slot *gfn_to_memslot_unaliased(struct kvm *kvm, gfn_t gfn);

arch/x86/kvm/emulate.c

+82 −7
Original line number Diff line number Diff line
@@ -1698,6 +1698,57 @@ emulate_sysexit(struct x86_emulate_ctxt *ctxt) 
	return 0;

}



static bool emulator_bad_iopl(struct x86_emulate_ctxt *ctxt)

{

	int iopl;

	if (ctxt->mode == X86EMUL_MODE_REAL)

		return false;

	if (ctxt->mode == X86EMUL_MODE_VM86)

		return true;

	iopl = (ctxt->eflags & X86_EFLAGS_IOPL) >> IOPL_SHIFT;

	return kvm_x86_ops->get_cpl(ctxt->vcpu) > iopl;

}



static bool emulator_io_port_access_allowed(struct x86_emulate_ctxt *ctxt,

					    struct x86_emulate_ops *ops,

					    u16 port, u16 len)

{

	struct kvm_segment tr_seg;

	int r;

	u16 io_bitmap_ptr;

	u8 perm, bit_idx = port & 0x7;

	unsigned mask = (1 << len) - 1;



	kvm_get_segment(ctxt->vcpu, &tr_seg, VCPU_SREG_TR);

	if (tr_seg.unusable)

		return false;

	if (tr_seg.limit < 103)

		return false;

	r = ops->read_std(tr_seg.base + 102, &io_bitmap_ptr, 2, ctxt->vcpu,

			  NULL);

	if (r != X86EMUL_CONTINUE)

		return false;

	if (io_bitmap_ptr + port/8 > tr_seg.limit)

		return false;

	r = ops->read_std(tr_seg.base + io_bitmap_ptr + port/8, &perm, 1,

			  ctxt->vcpu, NULL);

	if (r != X86EMUL_CONTINUE)

		return false;

	if ((perm >> bit_idx) & mask)

		return false;

	return true;

}



static bool emulator_io_permited(struct x86_emulate_ctxt *ctxt,

				 struct x86_emulate_ops *ops,

				 u16 port, u16 len)

{

	if (emulator_bad_iopl(ctxt))

		if (!emulator_io_port_access_allowed(ctxt, ops, port, len))

			return false;

	return true;

}



int

x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)

{
@@ -1889,6 +1940,11 @@ special_insn: 
		break;

	case 0x6c:		/* insb */

	case 0x6d:		/* insw/insd */

		if (!emulator_io_permited(ctxt, ops, c->regs[VCPU_REGS_RDX],

					  (c->d & ByteOp) ? 1 : c->op_bytes)) {

			kvm_inject_gp(ctxt->vcpu, 0);

			goto done;

		}

		if (kvm_emulate_pio_string(ctxt->vcpu,

				1,

				(c->d & ByteOp) ? 1 : c->op_bytes,
@@ -1905,6 +1961,11 @@ special_insn: 
		return 0;

	case 0x6e:		/* outsb */

	case 0x6f:		/* outsw/outsd */

		if (!emulator_io_permited(ctxt, ops, c->regs[VCPU_REGS_RDX],

					  (c->d & ByteOp) ? 1 : c->op_bytes)) {

			kvm_inject_gp(ctxt->vcpu, 0);

			goto done;

		}

		if (kvm_emulate_pio_string(ctxt->vcpu,

				0,

				(c->d & ByteOp) ? 1 : c->op_bytes,
@@ -2202,7 +2263,13 @@ special_insn: 
	case 0xef: /* out (e/r)ax,dx */

		port = c->regs[VCPU_REGS_RDX];

		io_dir_in = 0;

	do_io:	if (kvm_emulate_pio(ctxt->vcpu, io_dir_in,

	do_io:

		if (!emulator_io_permited(ctxt, ops, port,

					  (c->d & ByteOp) ? 1 : c->op_bytes)) {

			kvm_inject_gp(ctxt->vcpu, 0);

			goto done;

		}

		if (kvm_emulate_pio(ctxt->vcpu, io_dir_in,

				   (c->d & ByteOp) ? 1 : c->op_bytes,

				   port) != 0) {

			c->eip = saved_eip;
@@ -2227,13 +2294,21 @@ special_insn: 
		c->dst.type = OP_NONE;	/* Disable writeback. */

		break;

	case 0xfa: /* cli */

		if (emulator_bad_iopl(ctxt))

			kvm_inject_gp(ctxt->vcpu, 0);

		else {

			ctxt->eflags &= ~X86_EFLAGS_IF;

			c->dst.type = OP_NONE;	/* Disable writeback. */

		}

		break;

	case 0xfb: /* sti */

		if (emulator_bad_iopl(ctxt))

			kvm_inject_gp(ctxt->vcpu, 0);

		else {

			toggle_interruptibility(ctxt, X86_SHADOW_INT_STI);

			ctxt->eflags |= X86_EFLAGS_IF;

			c->dst.type = OP_NONE;	/* Disable writeback. */

		}

		break;

	case 0xfc: /* cld */

		ctxt->eflags &= ~EFLG_DF;

arch/x86/kvm/x86.c

+4 −6
Original line number Diff line number Diff line
@@ -3599,6 +3599,8 @@ int kvm_emulate_pio(struct kvm_vcpu *vcpu, int in, int size, unsigned port) 
{

	unsigned long val;



	trace_kvm_pio(!in, port, size, 1);



	vcpu->run->exit_reason = KVM_EXIT_IO;

	vcpu->run->io.direction = in ? KVM_EXIT_IO_IN : KVM_EXIT_IO_OUT;

	vcpu->run->io.size = vcpu->arch.pio.size = size;
@@ -3610,9 +3612,6 @@ int kvm_emulate_pio(struct kvm_vcpu *vcpu, int in, int size, unsigned port) 
	vcpu->arch.pio.down = 0;

	vcpu->arch.pio.rep = 0;



	trace_kvm_pio(vcpu->run->io.direction == KVM_EXIT_IO_OUT, port,

		      size, 1);



	if (!vcpu->arch.pio.in) {

		val = kvm_register_read(vcpu, VCPU_REGS_RAX);

		memcpy(vcpu->arch.pio_data, &val, 4);
@@ -3633,6 +3632,8 @@ int kvm_emulate_pio_string(struct kvm_vcpu *vcpu, int in, 
	unsigned now, in_page;

	int ret = 0;



	trace_kvm_pio(!in, port, size, count);



	vcpu->run->exit_reason = KVM_EXIT_IO;

	vcpu->run->io.direction = in ? KVM_EXIT_IO_IN : KVM_EXIT_IO_OUT;

	vcpu->run->io.size = vcpu->arch.pio.size = size;
@@ -3644,9 +3645,6 @@ int kvm_emulate_pio_string(struct kvm_vcpu *vcpu, int in, 
	vcpu->arch.pio.down = down;

	vcpu->arch.pio.rep = rep;



	trace_kvm_pio(vcpu->run->io.direction == KVM_EXIT_IO_OUT, port,

		      size, count);



	if (!count) {

		kvm_x86_ops->skip_emulated_instruction(vcpu);

		return 1;