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Subject[141/145] KVM: x86 emulator: Check CPL level during privilege instruction emulation
2.6.32-stable review patch.  If anyone has any objections, please let me know.

----------------
From: Gleb Natapov <gleb@redhat.com>

commit e92805ac1228626c59c865f2f4e9059b9fb8c97b upstream.

Add CPL checking in case emulator is tricked into emulating
privilege instruction from userspace.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86/kvm/emulate.c | 35 ++++++++++++++++++++---------------
1 file changed, 20 insertions(+), 15 deletions(-)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -75,6 +75,7 @@
#define Group (1<<14) /* Bits 3:5 of modrm byte extend opcode */
#define GroupDual (1<<15) /* Alternate decoding of mod == 3 */
#define GroupMask 0xff /* Group number stored in bits 0:7 */
+#define Priv (1<<27) /* instruction generates #GP if current CPL != 0 */
/* Source 2 operand type */
#define Src2None (0<<29)
#define Src2CL (1<<29)
@@ -204,7 +205,7 @@ static u32 opcode_table[256] = {
SrcNone | ByteOp | ImplicitOps, SrcNone | ImplicitOps,
/* 0xF0 - 0xF7 */
0, 0, 0, 0,
- ImplicitOps, ImplicitOps, Group | Group3_Byte, Group | Group3,
+ ImplicitOps | Priv, ImplicitOps, Group | Group3_Byte, Group | Group3,
/* 0xF8 - 0xFF */
ImplicitOps, 0, ImplicitOps, ImplicitOps,
ImplicitOps, ImplicitOps, Group | Group4, Group | Group5,
@@ -212,16 +213,20 @@ static u32 opcode_table[256] = {

static u32 twobyte_table[256] = {
/* 0x00 - 0x0F */
- 0, Group | GroupDual | Group7, 0, 0, 0, ImplicitOps, ImplicitOps, 0,
- ImplicitOps, ImplicitOps, 0, 0, 0, ImplicitOps | ModRM, 0, 0,
+ 0, Group | GroupDual | Group7, 0, 0,
+ 0, ImplicitOps, ImplicitOps | Priv, 0,
+ ImplicitOps | Priv, ImplicitOps | Priv, 0, 0,
+ 0, ImplicitOps | ModRM, 0, 0,
/* 0x10 - 0x1F */
0, 0, 0, 0, 0, 0, 0, 0, ImplicitOps | ModRM, 0, 0, 0, 0, 0, 0, 0,
/* 0x20 - 0x2F */
- ModRM | ImplicitOps, ModRM, ModRM | ImplicitOps, ModRM, 0, 0, 0, 0,
+ ModRM | ImplicitOps | Priv, ModRM | Priv,
+ ModRM | ImplicitOps | Priv, ModRM | Priv,
+ 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
/* 0x30 - 0x3F */
- ImplicitOps, 0, ImplicitOps, 0,
- ImplicitOps, ImplicitOps, 0, 0,
+ ImplicitOps | Priv, 0, ImplicitOps | Priv, 0,
+ ImplicitOps, ImplicitOps | Priv, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
/* 0x40 - 0x47 */
DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
@@ -313,9 +318,9 @@ static u32 group_table[] = {
SrcMem | ModRM | Stack, 0,
SrcMem | ModRM | Stack, 0, SrcMem | ModRM | Stack, 0,
[Group7*8] =
- 0, 0, ModRM | SrcMem, ModRM | SrcMem,
+ 0, 0, ModRM | SrcMem | Priv, ModRM | SrcMem | Priv,
SrcNone | ModRM | DstMem | Mov, 0,
- SrcMem16 | ModRM | Mov, SrcMem | ModRM | ByteOp,
+ SrcMem16 | ModRM | Mov | Priv, SrcMem | ModRM | ByteOp | Priv,
[Group8*8] =
0, 0, 0, 0,
DstMem | SrcImmByte | ModRM, DstMem | SrcImmByte | ModRM,
@@ -326,7 +331,7 @@ static u32 group_table[] = {

static u32 group2_table[] = {
[Group7*8] =
- SrcNone | ModRM, 0, 0, SrcNone | ModRM,
+ SrcNone | ModRM | Priv, 0, 0, SrcNone | ModRM,
SrcNone | ModRM | DstMem | Mov, 0,
SrcMem16 | ModRM | Mov, 0,
[Group9*8] =
@@ -1573,12 +1578,6 @@ emulate_sysexit(struct x86_emulate_ctxt
return -1;
}

- /* sysexit must be called from CPL 0 */
- if (kvm_x86_ops->get_cpl(ctxt->vcpu) != 0) {
- kvm_inject_gp(ctxt->vcpu, 0);
- return -1;
- }
-
setup_syscalls_segments(ctxt, &cs, &ss);

if ((c->rex_prefix & 0x8) != 0x0)
@@ -1642,6 +1641,12 @@ x86_emulate_insn(struct x86_emulate_ctxt
memcpy(c->regs, ctxt->vcpu->arch.regs, sizeof c->regs);
saved_eip = c->eip;

+ /* Privileged instruction can be executed only in CPL=0 */
+ if ((c->d & Priv) && kvm_x86_ops->get_cpl(ctxt->vcpu)) {
+ kvm_inject_gp(ctxt->vcpu, 0);
+ goto done;
+ }
+
if (((c->d & ModRM) && (c->modrm_mod != 3)) || (c->d & MemAbs))
memop = c->modrm_ea;




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