On 29/11/2014 16:27, Eugene Korenevsky wrote:
> Signed-off-by: Eugene Korenevsky <ekorenevsky@xxxxxxxxx>
> ---
>
> Notes:
> This patch adds checks on Guest RIP specified in Intel Software Developer Manual.
>
> The following checks are performed on processors that support Intel 64 architecture:
> - Bits 63:32 must be 0 if the "IA-32e mode guest" VM-entry control is 0 or if
> the L bit (bit 13) in the access-rights field for CS is 0.
> - If the processor supports N < 64 linear-address bits, bits 63:N must be identical
> if the "IA-32e mode guest" VM-entry control is 1 and the L bit in the access-rights
> field for CS is 1. (No check applies if the processor supports 64 linear-address
> bits.)
>
> arch/x86/kvm/vmx.c | 27 ++++++++++++++++++++++++++-
> 1 file changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 6a951d8..e2da83b 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3828,6 +3828,28 @@ static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
> (ss.selector & SELECTOR_RPL_MASK));
> }
>
> +#ifdef CONFIG_X86_64
> +static bool rip_valid(struct kvm_vcpu *vcpu)
> +{
> + unsigned long rip;
> + struct kvm_segment cs;
> + bool longmode;
> +
> + /* RIP must be canonical in long mode
> + * Bits 63:32 of RIP must be zero in other processor modes */
> + longmode = false;
> + if (vm_entry_controls_get(to_vmx(vcpu)) & VM_ENTRY_IA32E_MODE) {
> + vmx_get_segment(vcpu, &cs, VCPU_SREG_CS);
> + longmode = (cs.l != 0);
> + }
> + rip = kvm_register_read(vcpu, VCPU_REGS_RIP);
> + if (longmode)
> + return !is_noncanonical_address(rip);
This check is off by one. It is checking bits 63:47 instead of bits
63:48 (this quirk is intentionally part of the specification, so that
you can reenter a guest at 0x800000000000 after e.g. a VMCALL vmexit and
cause a general protection fault).
However, I am not sure how this can occur. A #GP should have been
injected as part of the instruction that caused RIP to become invalid.
Perhaps you should check in nested_vmx_run instead?
Paolo
> + else
> + return (rip >> 32) == 0;
> +}
> +#endif
> +
> /*
> * Check if guest state is valid. Returns true if valid, false if
> * not.
> @@ -3873,8 +3895,11 @@ static bool guest_state_valid(struct kvm_vcpu *vcpu)
> if (!ldtr_valid(vcpu))
> return false;
> }
> +#ifdef CONFIG_X86_64
> + if (!rip_valid(vcpu))
> + return false;
> +#endif
> /* TODO:
> - * - Add checks on RIP
> * - Add checks on RFLAGS
> */
>
>
My
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