From nobody Fri Oct 2 01:07:29 2026 Received: from mail-pj1-f72.google.com (mail-pj1-f72.google.com [209.85.216.72]) (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 C81D4483BF5 for ; Thu, 6 Aug 2026 17:06:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.72 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786035969; cv=none; b=l4Bf8jhh4EhpelXEQ8BaBAu+BS5/1DoObMIIdGylg1qbCO5f1Gib1FzgVqz+kU9vhqk0+VqI9l+C7Bxkvgpe5XkEeeCDgRv224X5LEGwtTPTDWHCI08kDhEbMcWbhroR4HqLZCr9GIPMlp5Ey6RNiFSTi6FjbXxDAv4YuCBNloY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786035969; c=relaxed/simple; bh=9rDKrntgrnlHH0gXwjE3RqLMQFAsGLVHx8ezzG+jCSQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=rSs2dASbnihmTWK3h2777WouzYgdzhQwpUxkciJ6AKv/ZLWIF+fiBWo3tc9kfZkoXH0ToFXjTnqQNLyQj/+otnpJVV1q5MIL7dKvroixM2++8jySivNj/UmfAh6hmm3lWrIe2djOL46LUV3r2LT93zmi5NdUFoS1xDzZr6KKpgg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=MencqOwJ; arc=none smtp.client-ip=209.85.216.72 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--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MencqOwJ" Received: by mail-pj1-f72.google.com with SMTP id 98e67ed59e1d1-3823dcc1647so3107861a91.3 for ; Thu, 06 Aug 2026 10:06:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786035966; x=1786640766; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:reply-to:from:to:cc:subject:date:message-id :reply-to:content-type; bh=Oa25XPOf9W3WEMkfc/K9a1heGuP5OTgCeX+yey0gIOM=; b=MencqOwJMhxlKxmeXCITC7xVe4niCx7pETArh2A5BPz+sM2p2qiATI4IsLaQnQM7qF zwZdOVjdKSUMTT/0Q9dvui7acY0oMmJgqFhC1gkFB1dyiIM+nEQmlKnIpAGtqSdZnwSN Zt8fQswLPBzoYmCGGr3WbpG+PhwukNXEPWlVaVo0G3m4nhUmhE2VIfW2LPGoabo0jKE3 Z570gzUpZLp/2voTcphXAAGIjiLguVxl51lYS7gikhc7VU4gvRNFSPDMPVwE6AQ+2Oqu KgsJWdvkL6IDWGoNjkkq2sGTDsUZhLpE/e0wT3j2pKgGSn9xhecMIMGC1RpdS/j4QN2+ aBjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786035966; x=1786640766; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:reply-to:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to:content-type; bh=Oa25XPOf9W3WEMkfc/K9a1heGuP5OTgCeX+yey0gIOM=; b=dVM9hLGpft6SbGpfo77xt2VHBhonSEhgClUaorsqaaytsgeX7l+ZmYOZFzhtWwjGxq JMRr93iszpFLe9ONkjG3wGicRV1OlzcMeU39STMAsY8i7hWAnlvEfnnCnNmBeKn3rwBj MfW1SYaPO2F1wCOIDfWGztlkzQvSmfCcpsPlzpojMlZcmDYRNJTDoKjrYICcKdY2cepC lc0OdMjYvkhjXwbDkju9+y/EgxyLCEKqG2MoLavQ/o7gZ3En33hcH9adPJuifgL4ADyL PhwISz9xgRYYpJF5Yr/YxvC/Svt6RmWOQ7LuPXdUqEMJnhd03DLsAItmRjZWzb171DL8 YtWA== X-Forwarded-Encrypted: i=1; AHgh+RotDxfDCVsVKAm7N4eaLXg+heN0UT/kxcsbkNlOrT77m24ruxq54mylBDQm2NbQF5D+lqXpf/QYxzRXAuY=@vger.kernel.org X-Gm-Message-State: AOJu0YwRPa/GYZp1g3DSM9qEX+HKoBXl0RPvi+qzJXRopPebOeqmje4w gJgVaYbBXcUgIdsZG8W+MoYEe/LNX82Q1TaHUcgZ0oWiU+qowyeCGZl6IpkRtppB79q8/g03LcU 6ZBBVPw== X-Received: from pjbtb8.prod.google.com ([2002:a17:90b:53c8:b0:37f:acb7:9d81]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:498b:b0:38e:7268:220d with SMTP id 98e67ed59e1d1-3903c628176mr18184487a91.20.1786035965922; Thu, 06 Aug 2026 10:06:05 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 6 Aug 2026 10:06:01 -0700 In-Reply-To: <20260806170602.4112602-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260806170602.4112602-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.679.g6767b8d81c-goog Message-ID: <20260806170602.4112602-2-seanjc@google.com> Subject: [PATCH v2 1/2] KVM: TDX: Reject INIT_MEM_REGION if number of bytes would overflow a u64 From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sashiko Bot , Yan Zhao , Binbin Wu , Ackerley Tng , Haotian Jiang Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Haotian Jiang The nr_pages field in struct kvm_tdx_init_mem_region is a u64 that comes directly from userspace via copy_from_user(). The current validation uses a manual overflow check: region.gpa + (region.nr_pages << PAGE_SHIFT) <=3D region.gpa When nr_pages >=3D 2^52, the shift (nr_pages << PAGE_SHIFT) wraps around to a small value, bypassing the wrap check. While downstream protections (gfn_to_memslot() returning NULL for GFNs outside any memslot, and kvm_slot_has_gmem() checking for NULL) prevent any actual out-of-bounds access, the overflow itself is a real bug that should be caught at the validation layer. Replace the manual overflow check with check_shl_overflow() to correctly detect the wrap-around. Note, the manual wrap-around check on the gpa+size technically has a benign off-by-one bug, and can also use check_add_overflow(). Those flaws will be addressed shortly. Opportunistically separate the initial sanity checks from the more involved checks to try and make the code easier to read. Fixes: c846b451d3c5 ("KVM: TDX: Add an ioctl to create initial guest memory= ") Reported-by: Sashiko Bot Closes: https://lore.kernel.org/all/20260630214952.98C851F000E9@smtp.kernel= .org Cc: Yan Zhao Cc: Binbin Wu Cc: Ackerley Tng Signed-off-by: Haotian Jiang [sean: use gpa_t, isolate check_shl_overflow() change, tweak changelog] Signed-off-by: Sean Christopherson Reviewed-by: Ackerley Tng Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao --- arch/x86/kvm/vmx/tdx.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index b272c20586a7..929115aeb9ec 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3219,6 +3219,7 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *= vcpu, struct kvm_tdx_cmd *c struct kvm_tdx *kvm_tdx =3D to_kvm_tdx(kvm); struct kvm_tdx_init_mem_region region; struct tdx_gmem_post_populate_arg arg; + gpa_t nr_bytes; long gmem_ret; int ret; =20 @@ -3236,10 +3237,13 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu= *vcpu, struct kvm_tdx_cmd *c return -EFAULT; =20 if (!PAGE_ALIGNED(region.source_addr) || !region.source_addr || - !PAGE_ALIGNED(region.gpa) || !region.nr_pages || - region.gpa + (region.nr_pages << PAGE_SHIFT) <=3D region.gpa || + !PAGE_ALIGNED(region.gpa) || !region.nr_pages) + return -EINVAL; + + if (check_shl_overflow(region.nr_pages, PAGE_SHIFT, &nr_bytes) || + region.gpa + nr_bytes <=3D region.gpa || !vt_is_tdx_private_gpa(kvm, region.gpa) || - !vt_is_tdx_private_gpa(kvm, region.gpa + (region.nr_pages << PAGE_SHI= FT) - 1)) + !vt_is_tdx_private_gpa(kvm, region.gpa + nr_bytes - 1)) return -EINVAL; =20 ret =3D 0; --=20 2.55.0.679.g6767b8d81c-goog From nobody Fri Oct 2 01:07:29 2026 Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) (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 F3A8748B368 for ; Thu, 6 Aug 2026 17:06:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.198 ARC-Seal: i=1; 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Thu, 06 Aug 2026 10:06:07 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 6 Aug 2026 10:06:02 -0700 In-Reply-To: <20260806170602.4112602-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260806170602.4112602-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.679.g6767b8d81c-goog Message-ID: <20260806170602.4112602-3-seanjc@google.com> Subject: [PATCH v2 2/2] KVM: TDX: Fix a benign off-by-one bug on the end GPA for INIT_MEM_REGION From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sashiko Bot , Yan Zhao , Binbin Wu , Ackerley Tng , Haotian Jiang Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When verifying that the incoming GPA rage for INIT_MEM_REGION doesn't wrap, check the inclusive last GPA, not the exclusive last GPA. Super duper technically, it's ok if the very last GPA is -1ull. In practice, the flaw is benign as KVM x86 disallows memslots with GPAs that exceed MAXPHYADDR, i.e. INIT_MEM_REGION would fail with -EINVAL anyways due to the memslot check in kvm_gmem_populate(). Opportunistically use check_add_overflow() instead of manually checking for wrap, mostly so that the inclusive math doesn't need to be copy+pasted in the "is private" check. Fixes: c846b451d3c5 ("KVM: TDX: Add an ioctl to create initial guest memory= ") Signed-off-by: Sean Christopherson Reviewed-by: Ackerley Tng Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao --- arch/x86/kvm/vmx/tdx.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 929115aeb9ec..85699ea021fe 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3219,7 +3219,7 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *= vcpu, struct kvm_tdx_cmd *c struct kvm_tdx *kvm_tdx =3D to_kvm_tdx(kvm); struct kvm_tdx_init_mem_region region; struct tdx_gmem_post_populate_arg arg; - gpa_t nr_bytes; + gpa_t nr_bytes, end_gpa; long gmem_ret; int ret; =20 @@ -3241,9 +3241,9 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *= vcpu, struct kvm_tdx_cmd *c return -EINVAL; =20 if (check_shl_overflow(region.nr_pages, PAGE_SHIFT, &nr_bytes) || - region.gpa + nr_bytes <=3D region.gpa || + check_add_overflow(region.gpa, nr_bytes - 1, &end_gpa) || !vt_is_tdx_private_gpa(kvm, region.gpa) || - !vt_is_tdx_private_gpa(kvm, region.gpa + nr_bytes - 1)) + !vt_is_tdx_private_gpa(kvm, end_gpa)) return -EINVAL; =20 ret =3D 0; --=20 2.55.0.679.g6767b8d81c-goog