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 0C697503BD4 for ; Fri, 4 Sep 2026 17:15:17 +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=1788542119; cv=none; b=JMhIXHLhnlwD6ZcS1dRQ7JJ6LKLMWfNhx73si2jwRmIIikDKucwlQUufEdMVQxb70os1JRknRfJYrQ+38vQfZrVJFocw6nLvsBGx0+/lSN7Qo9UhDmK7DJhuI3LcZ0M75qbgK/tjql3W16yilq8umAABGrdUl0geRv0PFZtx+KI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788542119; c=relaxed/simple; bh=gyz/gXAWDg6XnNqiPIcX2KIwSgp4rSVeIEHceOta9pM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=qWknpm4NVI+iQ++/WIvBCianGHzl76Lww8dIcwoVn8Q0oek/u9LQ0lP9QXQaEUxVlBR1pvelNE08b0spgt2JH12Qnux8cGC53RpyDcTaBgNPZadBUP7wL81QBwJtSHcl2CWyHCkaGQb0vKlJ+kv9P3OVueZCVdp2UraCYeJNYZw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WpYV42se; 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="WpYV42se" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA6671F00A3D; Fri, 4 Sep 2026 17:15:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788542117; bh=+De59R/iDVA6iu3+XB1FemyoSDqDvdDEmMkC+KZAfUo=; h=From:To:Cc:Subject:Date:Reply-To; b=WpYV42seepRGvObg/phcJLPsW8StTk4p/apRwyMJtcXHwA6bBYepc3oJKLH22Y7MB iTWHMdQcekIOPT7YjUY2dM+0vL5KCT1983Keww/YuqV69rDAoCE4KVOFQ0MB82YWAa Y3hlocYV2NuRyEyNdhE+NSKcfs8C5o5XFpXkkCzo= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80895: mshv: Order pt_vp_array publish against irqfd assertion path Date: Fri, 4 Sep 2026 19:09:36 +0200 Message-ID: <2026090430-CVE-2026-80895-4fcd@gregkh> X-Mailer: git-send-email 2.55.0 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=3811; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=TnNVKGKC98dpgBXaLp+83Vkr+Bduj8AoGQDhQ0MA+yE=; b=owGbwMvMwCRo6H6F97bub03G02pJDFmzfntNFFC8fvVmz8mWx418J+oy3b4IcmXJOKtt36Fj7 ZGfodfQEcvCIMjEICumyPJlG8/R/RWHFL0MbU/DzGFlAhnCwMUpABP5/5Rhwd7yoMwv4oV/NqVx FXPGxgV1ns5qZphfHqr8r1J3yjrmnP+s4s+fHb7ap5sEAA== 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: mshv: Order pt_vp_array publish against irqfd assertion path mshv_partition_ioctl_create_vp() initialises a VP struct (allocations, mutex_init, init_waitqueue_head, page mappings) and then publishes the pointer into partition->pt_vp_array. Several ISR paths read this array locklessly: the intercept ISR, the two scheduler ISRs, and mshv_try_assert_irq_fast() on the irqfd fast path. Of these, only mshv_try_assert_irq_fast() can structurally race the publish. It runs from an eventfd waker without holding pt_mutex, and MSHV_IRQFD does not require the target lapic_apic_id (== vp_index) to refer to an existing VP at registration time. A user can therefore register an irqfd targeting a yet-to-be-created VP, then trigger mshv_try_assert_irq_fast() concurrently with MSHV_CREATE_VP for the same index. On weakly-ordered architectures the reader can observe a non-NULL pointer in pt_vp_array before the initialising stores to the VP struct become visible, leading to use of partially-initialised fields (e.g. vp_register_page). The other ISR readers cannot reach this race: the hypervisor will not generate intercept or scheduler messages for a VP that has never been told to run, and the user can only call MSHV_RUN_VP on the VP fd returned by MSHV_CREATE_VP, which by construction is returned after the publish. Leave those readers as plain loads. Use smp_store_release() in mshv_partition_ioctl_create_vp() to publish the pointer, and pair it with smp_load_acquire() in mshv_try_assert_irq_fast(). On x86 these compile to plain accesses under TSO; on ARM64 they emit one-instruction acquire/release barriers, acceptable on this fast path. The destroy-side path (destroy_partition() clearing pt_vp_array[i] to NULL after kfree(vp)) has a separate ordering and lifetime concern that is out of scope here. The Linux kernel CVE team has assigned CVE-2026-80895 to this issue. Affected and fixed versions =========================== Issue introduced in 6.15 with commit 621191d709b14882270dfd8ea5d7d6cdfebe2c35 and fixed in 6.18.44 with commit 062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 Issue introduced in 6.15 with commit 621191d709b14882270dfd8ea5d7d6cdfebe2c35 and fixed in 7.1.8 with commit eba2bf5daa7933f94c53ebbbf0f567d4274716df Issue introduced in 6.15 with commit 621191d709b14882270dfd8ea5d7d6cdfebe2c35 and fixed in 7.2 with commit b098dc869219c15dc49bf9cf63fb5fc1481d3373 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-2026-80895 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: drivers/hv/mshv_eventfd.c drivers/hv/mshv_root_main.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/062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 https://git.kernel.org/stable/c/eba2bf5daa7933f94c53ebbbf0f567d4274716df https://git.kernel.org/stable/c/b098dc869219c15dc49bf9cf63fb5fc1481d3373