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Subject[054/197] KVM: x86 emulator: Check IOPL level during io instruction emulation
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------


From: Gleb Natapov <gleb@redhat.com>

commit f850e2e603bf5a05b0aee7901857cf85715aa694 upstream

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

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
arch/x86/include/asm/kvm_host.h | 1
arch/x86/kvm/emulate.c | 89 ++++++++++++++++++++++++++++++++++++----
arch/x86/kvm/x86.c | 10 +---
3 files changed, 87 insertions(+), 13 deletions(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -663,6 +663,7 @@ 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);

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1620,6 +1620,57 @@ emulate_sysexit(struct x86_emulate_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)
{
@@ -1779,7 +1830,12 @@ special_insn:
break;
case 0x6c: /* insb */
case 0x6d: /* insw/insd */
- if (kvm_emulate_pio_string(ctxt->vcpu, NULL,
+ 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, NULL,
1,
(c->d & ByteOp) ? 1 : c->op_bytes,
c->rep_prefix ?
@@ -1795,6 +1851,11 @@ 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, NULL,
0,
(c->d & ByteOp) ? 1 : c->op_bytes,
@@ -2094,7 +2155,13 @@ 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, NULL, 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, NULL, io_dir_in,
(c->d & ByteOp) ? 1 : c->op_bytes,
port) != 0) {
c->eip = saved_eip;
@@ -2119,13 +2186,21 @@ special_insn:
c->dst.type = OP_NONE; /* Disable writeback. */
break;
case 0xfa: /* cli */
- ctxt->eflags &= ~X86_EFLAGS_IF;
- c->dst.type = OP_NONE; /* Disable writeback. */
+ 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 */
- toggle_interruptibility(ctxt, X86_SHADOW_INT_STI);
- ctxt->eflags |= X86_EFLAGS_IF;
- c->dst.type = OP_NONE; /* Disable writeback. */
+ 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;
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3079,6 +3079,8 @@ int kvm_emulate_pio(struct kvm_vcpu *vcp
{
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;
@@ -3090,9 +3092,6 @@ int kvm_emulate_pio(struct kvm_vcpu *vcp
vcpu->arch.pio.down = 0;
vcpu->arch.pio.rep = 0;

- trace_kvm_pio(vcpu->run->io.direction == KVM_EXIT_IO_OUT, port,
- size, 1);
-
val = kvm_register_read(vcpu, VCPU_REGS_RAX);
memcpy(vcpu->arch.pio_data, &val, 4);

@@ -3111,6 +3110,8 @@ int kvm_emulate_pio_string(struct kvm_vc
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;
@@ -3122,9 +3123,6 @@ int kvm_emulate_pio_string(struct kvm_vc
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;



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