From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792759629; b=Uvf4Rsqg5a4bag0kZ6SUBOuI9jjM4UH358nK8JAQwOgHKCvFXwuGRLtk9+q3pNLXRERN 6mPMGdx7iFRdUxciQPTga48gMoE4y3scz2sBDDD0ufCs9Cpg/KWplkGkw6ZfZtamil3/H n+Cmq4ZXQ/hAfYIwoEuB9bMGmithmXyW1RzJIq0/7gk9fs1dniOo0d5Q8jA8lxIIsEaQz QYpI7Ck94J7BHNbCEuJevK5pAb0HEL95tNR469VBhYuIzJvpsu4uG+iTw/y4rbxrqyKUM L0qH2Ch3IRUs5WUWCuehZjDHEsGHGnJSPEQvt+cp+HLfCbUZvvEFOU/XeuIElmHBLlQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792759629; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: Reply-To:MIME-Version:Lines:X-Developer-Signature:X-Developer-Key: Content-Transfer-Encoding; bh=mw/UTlNOaIbDN6GT9ukTvcCFDLajF6y0rUOO/G0s9gQ=; b=sJGXb4mWF1jz5lyAouP5218iJCKBJeKbjutCv6Qm2b5Or6QA2QiqeGGkfeYiSvXd1dyL Z2iXxbRF5wviFn9xXs9Pu3YjkmbQoM46JXNryYD4ZMqRlpV6pxgB6fPd2Zaws+vEr8n8T 2Yfb0YYFxPVDTfoNRCLN9VcnRu1RSVTfa5mpxMznK0cnnfWnKsUxjnG7bzYKs33PuRRBJ WGotj6e8se0Kxdo1schGabmQvIMwqEcif1pYZM4/ZPbHoo2xdKluGb6fVvvg9AiAkr7Yz dE3/AFucSGB7uegSnaa/WzuVoY+ROv73UwXmGd1RO02+eJ6A56D7nZCT5OjsdX1SAxw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b="SgT2Q/cX"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 93DD6606A320 for ; Fri, 23 Oct 2026 12:47:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=SgT2Q/cX Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3F6D1F01825; Fri, 23 Oct 2026 12:47:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792759629; bh=mw/UTlNOaIbDN6GT9ukTvcCFDLajF6y0rUOO/G0s9gQ=; h=From:To:Cc:Subject:Date:Reply-To; b=SgT2Q/cXSzsXRbbvRbDP1YlKq/VOozJfOmoXCWYn/auqQl2szOm5XJ5YlVhZlm+/1 7RiwMvTSD7LQrUJNAdJkSPVXd++TcFSURQmY+9y+rFpAdKEMTB6sd09fHNrJqPMGY2 e+UGSOQtLDGMl0Ep2dc2vk0StrRNifix7XShlZT8= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-99082: KVM: x86: Use active memslots for the per-vCPU MMIO cache Date: Fri, 23 Oct 2026 14:45:15 +0200 Message-ID: <2026102314-CVE-2026-99082-e5b1@gregkh> X-Mailer: git-send-email 2.56.0 Reply-To: , X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4380; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=rwDcT/54+ZO5IcnjFvOaMT7VXnfepPQUzvfJohlJJ8M=; b=owGbwMvMwCRo6H6F97bub03G02pJDFm3w26V73vLe4sj65m/yXmTLzxRlaZe+4Ov8afdvfF27 dfzl3wTO2JZGASZGGTFFFm+bOM5ur/ikKKXoe1pmDmsTCBDGLg4BWAibzQYFixNYBHTiFv6vKiv vfrT5PyzYgcMyhnm2Wn8llm7dyL3tZhp7zZPvcNTcP88PwA= 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: Use active memslots for the per-vCPU MMIO cache KVM tags the per-vCPU MMIO cache with a memslot generation so that a memslot update invalidates cached MMIO information. Both the fill and validation paths use kvm_memslots(), which unconditionally selects address space 0, even when the vCPU is running in SMM and using address space 1. Commit 56f17dd3fbc4 ("kvm: x86: fix stale mmio cache bug") added the memslot generation to the cache key so that a memslot update could not leave a stale entry valid. When commit 699023e23965 ("KVM: x86: add SMM to the MMU role, support SMRAM address space") added the SMM address space, these helpers were not converted to use the active memslots. Consequently, an update to the SMM memslots can leave an entry from the old SMM address space apparently valid after the vCPU returns to the normal address space. A guest can then cause an access to valid RAM at the same GFN to be returned to userspace as KVM_EXIT_MMIO. Completing that exit through the VMM's RAM address space writes the backing page without going through KVM's write-tracking path. If the page backs a nested EPT table, KVM can continue using shadow translations derived from the old contents. The WARN_ON_ONCE() in kvm_mmu_write_protect_fault() catches this invalid cache and memslot combination. Use the vCPU's active memslots when caching and validating the entry. Memslot generations are unique across address spaces, so the generation also distinguishes the normal and SMM views. This matches the MMIO SPTE cache, which already uses kvm_vcpu_memslots(). On an unpatched current-mainline kernel, a regression test that fills the cache in SMM and updates only the SMM memslots fails the intended RAM write and triggers the kvm_mmu_write_protect_fault() warning. With this change, the same test completes the RAM write without a warning. The x86/smm_test, set_memory_region_test, and memslot_modification_stress_test selftests also pass. The Linux kernel CVE team has assigned CVE-2026-99082 to this issue. Affected and fixed versions =========================== Issue introduced in 4.2 with commit 699023e239658e62da6f42f47d31b54788521ec1 and fixed in 6.6.160 with commit a63f79d9da9468952396af73e1e53330845cf876 Issue introduced in 4.2 with commit 699023e239658e62da6f42f47d31b54788521ec1 and fixed in 6.12.114 with commit 7fd4e64f4bbc8c35ae8f0d2a1fb5b77a76d5b4fd Issue introduced in 4.2 with commit 699023e239658e62da6f42f47d31b54788521ec1 and fixed in 6.18.58 with commit 2566780c684c9c21241d409d790087c73070f312 Issue introduced in 4.2 with commit 699023e239658e62da6f42f47d31b54788521ec1 and fixed in 7.2.12 with commit e792a9ace39d2812a5b342a1987186c7bc653204 Issue introduced in 4.2 with commit 699023e239658e62da6f42f47d31b54788521ec1 and fixed in 7.3 with commit b3e6212dea2e4328a841ceb37f377583176dc735 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-2026-99082 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/x86.h 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/a63f79d9da9468952396af73e1e53330845cf876 https://git.kernel.org/stable/c/7fd4e64f4bbc8c35ae8f0d2a1fb5b77a76d5b4fd https://git.kernel.org/stable/c/2566780c684c9c21241d409d790087c73070f312 https://git.kernel.org/stable/c/e792a9ace39d2812a5b342a1987186c7bc653204 https://git.kernel.org/stable/c/b3e6212dea2e4328a841ceb37f377583176dc735