linux-kernel - Re: [PATCH RFC v9 29/51] KVM: SVM: Add KVM_SEV_SNP_LAUNCH

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Date:   Mon, 12 Jun 2023 11:08:11 -0600
From:   Peter Gonda <pgonda@...gle.com>
To:     Michael Roth <michael.roth@....com>
Cc:     kvm@...r.kernel.org, linux-coco@...ts.linux.dev,
        linux-mm@...ck.org, linux-crypto@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
        ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        vkuznets@...hat.com, jmattson@...gle.com, luto@...nel.org,
        dave.hansen@...ux.intel.com, slp@...hat.com, peterz@...radead.org,
        srinivas.pandruvada@...ux.intel.com, rientjes@...gle.com,
        dovmurik@...ux.ibm.com, tobin@....com, bp@...en8.de,
        vbabka@...e.cz, kirill@...temov.name, ak@...ux.intel.com,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
        dgilbert@...hat.com, jarkko@...nel.org, ashish.kalra@....com,
        nikunj.dadhania@....com, liam.merwick@...cle.com,
        zhi.a.wang@...el.com, Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH RFC v9 29/51] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command

> +
> +static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{
> +       struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +       struct sev_data_snp_launch_start start = {0};
> +       struct kvm_sev_snp_launch_start params;
> +       int rc;
> +
> +       if (!sev_snp_guest(kvm))
> +               return -ENOTTY;
> +
> +       if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
> +               return -EFAULT;
> +
> +       sev->snp_context = snp_context_create(kvm, argp);
> +       if (!sev->snp_context)
> +               return -ENOTTY;


I commented on a  previous series but I think the bug is still here. I
think users can repeatedly call KVM_SEV_SNP_LAUNCH_START to have KVM
keep allocating more snp_contexts above.

Should we check if the VM already has a |snp_context| and error out if so?

>
> +
> +       start.gctx_paddr = __psp_pa(sev->snp_context);
> +       start.policy = params.policy;
> +       memcpy(start.gosvw, params.gosvw, sizeof(params.gosvw));
> +       rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_START, &start, &argp->error);
> +       if (rc)
> +               goto e_free_context;
> +
> +       sev->fd = argp->sev_fd;
> +       rc = snp_bind_asid(kvm, &argp->error);
> +       if (rc)
> +               goto e_free_context;
> +
> +       return 0;
> +
> +e_free_context:
> +       snp_decommission_context(kvm);
> +
> +       return rc;
> +}
> +