linux-kernel - Re: [PATCH v2 10/11] KVM: x86: SVM: use smram structs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 21 Jul 2022 14:54:38 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org, x86@...nel.org,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v2 10/11] KVM: x86: SVM: use smram structs

On Thu, 2022-07-21 at 00:18 +0000, Sean Christopherson wrote:
> On Tue, Jun 21, 2022, Maxim Levitsky wrote:
> > This removes the last user of put_smstate/GET_SMSTATE so
> > remove these functions as well.
> > 
> > Also add a sanity check that we don't attempt to enter the SMM
> > on non long mode capable guest CPU with a running nested guest.
> > 
> > Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h |  6 ------
> >  arch/x86/kvm/svm/svm.c          | 28 +++++++++++++++++-----------
> >  2 files changed, 17 insertions(+), 17 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 1038ccb7056a39..9e8467be96b4e6 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -2057,12 +2057,6 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
> >  #endif
> >  }
> >  
> > -#define put_smstate(type, buf, offset, val)                      \
> > -	*(type *)((buf) + (offset) - 0x7e00) = val
> > -
> > -#define GET_SMSTATE(type, buf, offset)		\
> > -	(*(type *)((buf) + (offset) - 0x7e00))
> > -
> >  int kvm_cpu_dirty_log_size(void);
> >  
> >  int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages);
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index 136298cfb3fb57..8dcbbe839bef36 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -4399,6 +4399,7 @@ static int svm_smi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
> >  
> >  static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
> >  {
> > +	struct kvm_smram_state_64 *smram = (struct kvm_smram_state_64 *)smstate;
> >  	struct vcpu_svm *svm = to_svm(vcpu);
> >  	struct kvm_host_map map_save;
> >  	int ret;
> > @@ -4406,10 +4407,17 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
> >  	if (!is_guest_mode(vcpu))
> >  		return 0;
> >  
> > -	/* FED8h - SVM Guest */
> > -	put_smstate(u64, smstate, 0x7ed8, 1);
> > -	/* FEE0h - SVM Guest VMCB Physical Address */
> > -	put_smstate(u64, smstate, 0x7ee0, svm->nested.vmcb12_gpa);
> > +	/*
> > +	 * 32 bit SMRAM format doesn't preserve EFER and SVM state.
> > +	 * SVM should not be enabled by the userspace without marking
> > +	 * the CPU as at least long mode capable.
> > +	 */
> > +
> > +	if (!guest_cpuid_has(vcpu, X86_FEATURE_SVM))
> > +		return 1;
> 
> Isn't this is an independent bug fix?  I.e. should be in its own patch?

Yes to some extent, patch was small so I didn't bother, but I don't mind splitting it up.

Best regards,
	Maxim Levitsky

> 
> > +
> > +	smram->svm_guest_flag = 1;
> > +	smram->svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa;
> >  
> >  	svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];
> >  	svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP];