| Date | Tue, 30 Mar 2010 15:48:46 -0700 | From | Greg KH <> | Subject | [26/45] KVM: x86 emulator: limit instructions to 15 bytes |
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2.6.27-stable review patch. If anyone has any objections, please let us know.
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commit eb3c79e64a70fb8f7473e30fa07e89c1ecc2c9bb upstream
[ <cebbert@redhat.com>: backport to 2.6.27 ]
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.
Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/x86/kvm/x86_emulate.c | 5 ++++- include/asm-x86/kvm_x86_emulate.h | 2 +- 2 files changed, 5 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/x86_emulate.c +++ b/arch/x86/kvm/x86_emulate.c @@ -581,6 +581,9 @@ static int do_insn_fetch(struct x86_emul { 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++); @@ -839,7 +842,7 @@ x86_decode_insn(struct x86_emulate_ctxt /* Shadow copy of register state. Committed on successful emulation. */ memset(c, 0, sizeof(struct decode_cache)); - c->eip = ctxt->vcpu->arch.rip; + c->eip = c->eip_orig = ctxt->vcpu->arch.rip; ctxt->cs_base = seg_base(ctxt, VCPU_SREG_CS); memcpy(c->regs, ctxt->vcpu->arch.regs, sizeof c->regs); --- a/include/asm-x86/kvm_x86_emulate.h +++ b/include/asm-x86/kvm_x86_emulate.h @@ -128,7 +128,7 @@ 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;
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