From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f200.google.com (mail-pl1-f200.google.com [209.85.214.200]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EA1933DA7EC for ; Thu, 10 Sep 2026 21:06:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789074412; cv=none; b=ApQirL4XLUX+LoTk8xeG2vD0irDEti4GgcEVFLlXwQOh4FyQ+XZUGHPH5Im0j/DD9prbbXslbJBVON+28e5M58pgi8IQOf0Prjb7wfAAJGYq97bHopv3QuLWBGUCpxxyAAbZKRrkgT5+OSHUVJ3Y3xB0Kzq6cnucRMqKZ1C9iIk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789074412; c=relaxed/simple; bh=+QJuiFNNU2WuMiOfbuoDhSNfC8EPo0OvHi6oF2IXUBk=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=soM4hd0Ej9DA0+wF19xuDusI1ostpUmtKXvpuidzTpKgMj6KE8w8HpmD65eSHtkcEyOM+EdPplmOmjQdsa34b20QyECvSfIMwRqK76zGQiw+TKqC5G+MXWci0fdDtFqHKl+q6NnK8s0I7Toi9c5fqR2CugeCFE0lktJXYHMHERk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jackyli.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=lDfDQ60A; arc=none smtp.client-ip=209.85.214.200 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jackyli.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lDfDQ60A" Received: by mail-pl1-f200.google.com with SMTP id d9443c01a7336-2d54187d8b0so3187675ad.0 for ; Thu, 10 Sep 2026 14:06:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789074403; x=1789679203; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=gNFeNcyltUj1f0y6EIQIHeGiYuc25QrluAzkIS54884=; b=lDfDQ60A/xRzIoOlqH9MAGMnIsM9B8IGS2CfdNOxxigbqzgsDTFtrf5OH+ZoOUeG0A ddvM4MTBojzhq0mwKOaA6w7LtBAY4aGrwktu/0j/PFZrG2/fY5m8Ws5BpxJLjY9PdLKJ /Y3384bV2v9+LkmF68Kjk7/chXhXNjTq+1Qo1jdfj6Z2AyYmt1zeLUX1iKm63FIgIU7N txlCD5H8XFYH+q8BTcvfZLm+WvsVCqGlyDnTY7MwTzLwhx/ThBupEAW7qTHHOEFxW3kb in90wpgqOX4HqT7KgceJ4cp537vBnwQzkMQ+Rg1P2q/s+gv4F9B+qVMLXChZ1n1BHMS6 xFsQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1789074403; x=1789679203; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=gNFeNcyltUj1f0y6EIQIHeGiYuc25QrluAzkIS54884=; b=E/ltSA1vj8ErHi4AEW4OhV7z0Q6VtqA/vMNk4uqNaWMEQMB1P1jg8kqOXVj/2aLPa6 9FDd4R6DlA9wSBol07Lag3NgZhDWgTJlgI0gFCVlNwar+Sk2PD/15fRxO/GS+YzO75Tc Amh/q9NYh3rxoF2RC+PaTTqDYGpThZFZYHA09o883TFq+/xJwAZ8h0wfZ0Y0tej7+R5N cZKjf7jceATG0L8zmQVX5nJ1QiZ4imGp6XoXWzPLhm413Hsfx6GhgeTFIBUjHzOP1fVu 7K2Vzsi2el2iGNeQkucZ6hiMQxvWP2o89oD3mZGu64T99ydn2junA+4/Y6x4+vWO2orl fdPA== X-Forwarded-Encrypted: i=1; AKwUvBzlfohU+JJoYop0k0cBrgMLzu2SN9oS5JGSJ8oo/6W3oTTwEj2BIVmOzh2csU6itdSZmkVXcbZbYfhzBDc=@vger.kernel.org X-Gm-Message-State: AFuF++nd3OmP3kLQ6S44n7YsLw34rgq/SsS734nw8ktrPiCvHaLMKMMC +K4QVb0lb1+b3NpbUr9Gfj/TEcZxEIikdiT2qsvQf+S6e7U3CbErACYO2jW+OmdLOdbNM6MboHy ethQzBd8Q X-Received: from pleg20.prod.google.com ([2002:a17:902:e394:b0:2db:814a:e864]) (user=jackyli job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ea03:b0:2d9:1dee:43db with SMTP id d9443c01a7336-2dd2a34fd9cmr23427655ad.15.1789074402904; Thu, 10 Sep 2026 14:06:42 -0700 (PDT) Date: Thu, 10 Sep 2026 21:06:21 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAMwbo2oC/x2MSwqAIBQArxJvnaBR9rlKtNB81oMw0ZJAunvSa pjFTIaIgTDCVGUImCjS6YqIuoJ1V25DRqY4NLyRfBScRecZuaQOMoX+vlhntJaq5QP2FkrnA1p 6/ue8vO8HL8zzAGMAAAA= X-Change-Id: 20260910-snp-invalid-input-5dbb6a408e7f X-Mailer: b4 0.14.3 Message-ID: <20260910-snp-invalid-input-v1-1-fb2e03da614b@google.com> Subject: [PATCH] KVM: SEV: Return INVALID_INPUT on SNP req/resp buffer access failure From: Jacky Li To: kvm@vger.kernel.org Cc: Sean Christopherson , Paolo Bonzini , Tom Lendacky , Michael Roth , Ashish Kalra , Jacob Xu , Supraja Sridhara , linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, Jacky Li Content-Type: text/plain; charset="utf-8" Currently, snp_handle_(ext_)guest_req() returns -EIO when kvm_{read/write/clear}_guest() fails while accessing guest-provided buffers. Returning -EIO causes KVM_RUN to exit to userspace, likely killing the VM. Fix this by returning GHCB_HV_RESP_MALFORMED_INPUT with sub-error code GHCB_ERR_INVALID_INPUT to the guest and resuming the vCPU. Per the GHCB specification, guest-provided GPA buffers that cannot be accessed by the hypervisor (e.g. private pages) should be treated as guest input errors. Because kvm_{read/write/clear}_guest() only returns -EFAULT on failure, treating this failure as an invalid input aligns with the definition of -EFAULT ("Bad address"). Returning GHCB_ERR_INVALID_INPUT also matches existing SNP handling in KVM, which already returns this error code for unaligned or overlapping buffers. It also aligns with other hypercall implementations in KVM (e.g. Hyper-V returning INVALID_HYPERCALL_INPUT on kvm_read_guest() failures in kvm_hv_flush_tlb()). Performing upfront validation (e.g. via kvm_mem_is_private()) is avoided because it is prone to TOCTOU races with concurrent Page State Changes. Fixes: 88caf544c930 ("KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event") Fixes: 74458e4859d8 ("KVM: SEV: Provide support for SNP_EXTENDED_GUEST_REQUEST NAE event") Signed-off-by: Jacky Li --- arch/x86/kvm/svm/sev.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 5705723f1f41..d07562310519 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -4228,8 +4228,10 @@ static int snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_ guard(mutex)(&sev->guest_req_mutex); - if (kvm_read_guest(kvm, req_gpa, sev->guest_req_buf, PAGE_SIZE)) - return -EIO; + if (kvm_read_guest(kvm, req_gpa, sev->guest_req_buf, PAGE_SIZE)) { + svm_vmgexit_bad_input(svm, GHCB_ERR_INVALID_INPUT); + return 1; + } data.gctx_paddr = __psp_pa(sev->snp_context); data.req_paddr = __psp_pa(sev->guest_req_buf); @@ -4244,8 +4246,10 @@ static int snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_ if (ret && !fw_err) return ret; - if (kvm_write_guest(kvm, resp_gpa, sev->guest_resp_buf, PAGE_SIZE)) - return -EIO; + if (kvm_write_guest(kvm, resp_gpa, sev->guest_resp_buf, PAGE_SIZE)) { + svm_vmgexit_bad_input(svm, GHCB_ERR_INVALID_INPUT); + return 1; + } /* No action is requested *from KVM* if there was a firmware error. */ svm_vmgexit_no_action(svm, SNP_GUEST_ERR(0, fw_err)); @@ -4296,7 +4300,7 @@ static int snp_handle_ext_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t r if (kvm_read_guest(kvm, req_gpa + offsetof(struct snp_guest_msg_hdr, msg_type), &msg_type, 1)) - return -EIO; + goto request_invalid; /* * As per GHCB spec, requests of type MSG_REPORT_REQ also allow for @@ -4336,7 +4340,7 @@ static int snp_handle_ext_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t r * certificate table is terminated by 24-bytes of zeroes. */ if (data_npages && kvm_clear_guest(kvm, data_gpa, 24)) - return -EIO; + goto request_invalid; } return snp_handle_guest_req(svm, req_gpa, resp_gpa); --- base-commit: 50d05c7c76c96b90462f24debacca971d2e86713 change-id: 20260910-snp-invalid-input-5dbb6a408e7f Best regards, -- Jacky Li