From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2EB563C0611 for ; Sun, 18 Oct 2026 15:53:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792338839; cv=none; b=C3cSvQuzwRZF0UbaPrnH9Nx80sWmnlh8VPVOdDLFxcuq9Q+aUQw9CTh33xbhiCf9sD65A1flktjk72KX44qMhenRjCetJMRgRnK2AEZ1J0RA3HoWpDsKzAGcOhVf7bbbiHGGbCkX10GuGpnXBd2X7fFQtFrRnzyptoAB5rtn1mo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792338839; c=relaxed/simple; bh=QueLW7oW/mfCPDtLEVI6QAJa4IO3hjob28uXGke7Kts=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=W54H8zd7iQ8Lso6NkQx/Q3efxZY1VMVqtzuXdUjGk8caDq2aiZYm5RuB5le3RrVS3AW12aCAJ6Q6MGM6GoUzlS9jhhgLINMV5QOm/rJddkOxmQBt0YNNEt+5PHnTRslqkX0o31LcMi04NKhWu4joevNfF4lkGL+hvalf4kThSu0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=MLlQOKzG; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="MLlQOKzG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 049CD1F000C4; Sun, 18 Oct 2026 15:53:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792338837; bh=9wsOjDTZ7xi9fMSCiIMC6iv0eRjimqTGG0pnBBDCTgo=; h=From:To:Cc:Subject:Date:Reply-To; b=MLlQOKzGleVnRDPJ7bWJHzmSjJNmuxv6I4TeGwp/XOV8JnP1u0xtU3JgvLBOmD1MC 0LXpukIqZmLCh0tF010QyK9ApAsftwqlQQ4Ngn7X3iaKhX9BLKvTHJOyGmo7oBRWwD K1fd/inMykyl/EowFSbkKjtoFhUi0lJyRrw3p0/U= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-98717: KVM: x86/mmu: Bail from shadow walks if the root is invalid or a dummy Date: Sun, 18 Oct 2026 17:44:52 +0200 Message-ID: <2026101808-CVE-2026-98717-fd17@gregkh> X-Mailer: git-send-email 2.56.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4279; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=Amcw65OvQLxKuHt8beKd9qp5vhuHVdbO+8/FX2//6f4=; b=kA0DAAIRMUfUDdst+ykByyZiAGrU6UiguDF5uhnKszvJibCHNawfixtCxNpLX7W2IzCImoH+U ohdBAARAgAdFiEE9LYMxb94wiFKMT3LMUfUDdst+ykFAmrU6UgACgkQMUfUDdst+yklUACeJaUN 58koxVwbFOLJcrGPZcVqQA8An3WkmuBvYazRFDufY1I9XjIKA3cb X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: KVM: x86/mmu: Bail from shadow walks if the root is invalid or a dummy When walking shadow page tables, immediately terminate the walk if the root is a "dummy" root, i.e. a root whose top-level page table is backed by the zero page, but otherwise doesn't exist. If memslot creation races with a stage-2 page fault (EPT violation or #NPF) from L2, then if the stars align, KVM will attempt to walk shadow page tables using the zero page and hit a NULL pointer deref. BUG: kernel NULL pointer dereference, address: 0000000000000021 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP CPU: 30 UID: 1000 PID: 941 Comm: qemu Not tainted 7.2.0-rc2-1b731e5ded48-next-vm #1741 PREEMPTLAZY Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:__kvm_mmu_invalidate_addr+0xea/0x210 [kvm] Call Trace: kvm_mmu_invalidate_addr+0x92/0xe0 [kvm] __kvm_inject_emulated_page_fault+0x67/0x80 [kvm] ept_page_fault+0x160/0x850 [kvm] kvm_mmu_do_page_fault+0x102/0x1f0 [kvm] kvm_mmu_page_fault+0x8e/0x6b0 [kvm] vmx_handle_exit+0x163/0x640 [kvm_intel] kvm_arch_vcpu_ioctl_run+0x960/0x2120 [kvm] kvm_vcpu_ioctl+0x2c7/0x970 [kvm] __x64_sys_ioctl+0x90/0xd0 do_syscall_64+0x67/0x5f0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f606d0b53bb Opportunistically harden the shadow walks against fully invalid roots, but WARN, as all callers are expected/required to pre-check for a valid root. Don't WARN in the dummy root case as the whole point of using a dummy root is to provide a root that's valid enough to enter the guest, i.e. it should Just Work for all flows except those that *need* to know about dummy roots. Alternatively, KVM could allocate a dedicated page and associated shadow page structure for the dummy root, which is very tempting as it such an approach should be more resilient against unexpected behavior. But that would be a much larger and thus riskier change than simply terminating walks of dummy roots. The Linux kernel CVE team has assigned CVE-2026-98717 to this issue. Affected and fixed versions =========================== Issue introduced in 6.6 with commit 0e3223d8d00ac05849661f1b8b476d3caca251cf and fixed in 6.12.113 with commit e1bcabc07efd029ab414894127411129ffdb8b48 Issue introduced in 6.6 with commit 0e3223d8d00ac05849661f1b8b476d3caca251cf and fixed in 6.18.56 with commit 97c1dcce17ef27853860c781f9912257e6adbf7c Issue introduced in 6.6 with commit 0e3223d8d00ac05849661f1b8b476d3caca251cf and fixed in 7.2.10 with commit 681e31f03ec9219099a66a0f6e1bc48e1b5aa914 Issue introduced in 6.6 with commit 0e3223d8d00ac05849661f1b8b476d3caca251cf and fixed in 7.3-rc6 with commit b6249c1d5665098c8bf12f8d3e4712bf04c775bc Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-98717 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: arch/x86/kvm/mmu/mmu.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/e1bcabc07efd029ab414894127411129ffdb8b48 https://git.kernel.org/stable/c/97c1dcce17ef27853860c781f9912257e6adbf7c https://git.kernel.org/stable/c/681e31f03ec9219099a66a0f6e1bc48e1b5aa914 https://git.kernel.org/stable/c/b6249c1d5665098c8bf12f8d3e4712bf04c775bc