aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorAvi Kivity <avi@redhat.com>2009-11-24 15:20:15 +0200
committerAvi Kivity <avi@redhat.com>2009-12-03 09:32:25 +0200
commiteb3c79e64a70fb8f7473e30fa07e89c1ecc2c9bb (patch)
treee6c73345d26a553d0b36a9503d674fd70b66233d
parentd7b0b5eb3000c6fb902f08c619fcd673a23d8fab (diff)
KVM: x86 emulator: limit instructions to 15 bytes
While we are never normally passed an instruction that exceeds 15 bytes, smp games can cause us to attempt to interpret one, which will cause large latencies in non-preempt hosts. Cc: stable@kernel.org Signed-off-by: Avi Kivity <avi@redhat.com>
-rw-r--r--arch/x86/include/asm/kvm_emulate.h2
-rw-r--r--arch/x86/kvm/emulate.c5
2 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index b7ed2c42311..7c18e1230f5 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -129,7 +129,7 @@ struct decode_cache {
u8 seg_override;
unsigned int d;
unsigned long regs[NR_VCPU_REGS];
- unsigned long eip;
+ unsigned long eip, eip_orig;
/* modrm */
u8 modrm;
u8 modrm_mod;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index d226dff47d7..7e8faea4651 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -622,6 +622,9 @@ static int do_insn_fetch(struct x86_emulate_ctxt *ctxt,
{
int rc = 0;
+ /* x86 instructions are limited to 15 bytes. */
+ if (eip + size - ctxt->decode.eip_orig > 15)
+ return X86EMUL_UNHANDLEABLE;
eip += ctxt->cs_base;
while (size--) {
rc = do_fetch_insn_byte(ctxt, ops, eip++, dest++);
@@ -880,7 +883,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
/* Shadow copy of register state. Committed on successful emulation. */
memset(c, 0, sizeof(struct decode_cache));
- c->eip = kvm_rip_read(ctxt->vcpu);
+ c->eip = c->eip_orig = kvm_rip_read(ctxt->vcpu);
ctxt->cs_base = seg_base(ctxt, VCPU_SREG_CS);
memcpy(c->regs, ctxt->vcpu->arch.regs, sizeof c->regs);