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 5627038B14D for ; Sat, 15 Aug 2026 06:40:41 +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=1786776042; cv=none; b=jJBSUJ7F1SSgPU+1va6P4bVzUtW+qunSoNveD3bX1Wxnt3DzUin/+bZnKrnyt/boQY40Ue65mwMJOTgE6fFdplduvbfRgdE6RsPr11e2BKwGXPqQsK35MBLynH452Y+0HT4Hybr7M2tNZdqr/b7nHbU6JqWj8tS+P/dl5goL7fI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786776042; c=relaxed/simple; bh=w+78H3/PcqazgOrCzmw0EkjD8ecQs3fJjE1hXGyeR1Y=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=YY+fZIdHAq4WVAPEUtnH28t/CoQNiXmh8Y7FJAvsMvRdMEQQAGtAOfQXpJblI1TEBpxPvSyFixINa8Z8w6mmqozoCs6MWnYle4NC3Lx4nefBlfqP/ytrE8tcFr4e7bgIfclwNnV+sx6ceRA+2LmZ6glg3FK2VlTa5LwqxSo7AbA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=MBsBBb3g; 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="MBsBBb3g" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 646BA1F000E9; Sat, 15 Aug 2026 06:40:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786776041; bh=Ev/+oyww+3noFHp/mzILshbFE/nAD1EdbP1MhH2tTio=; h=From:To:Cc:Subject:Date:Reply-To; b=MBsBBb3g1Ejk5tM+jE/FW/Ugkm9rdH7/BaQrIol4VJx0aqM1sbl4mXBeexdM1Yoqn ZNXVAX7dmqpHiJ7pUgnTqd3LY+1+xgrcOLCXb04sXs/NqPX3xrAaGLe+/ecIQglzLe J9igEDtSu+KxC8aU7/c/LLXzfr7Xf8cnsWPnFjUI= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-74439: iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry Date: Sat, 15 Aug 2026 15:12:46 +0900 Message-ID: <2026081516-CVE-2026-74439-1deb@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=3598; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=+72wo2IltaC156XpCVRyk/0TohvR9dKEhUnJZlGilyc=; b=owGbwMvMwCRo6H6F97bub03G02pJDFkNjCqNtr95zxjvPDW9Llvi0XKvlidv5cKdm1JW79K7n vHD7detjlgWBkEmBlkxRZYv23iO7q84pOhlaHsaZg4rE8gQBi5OAZgI52+GeTq2Qf/qHvXNZ/x+ b6LwNsEQXQ2jVIYFS1srZ0qW+t1dyzAppjbENUW3ovQcAA== 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: iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry device_pasid_table_teardown() zeroes the 128-bit scalable-mode context entry with context_clear_entry() while the Present bit is still set. This creates a window where the hardware can fetch a torn entry, with some fields already zeroed while Present is still set, leading to unpredictable behavior or spurious faults. The context-cache invalidation is issued only after the entry has been zeroed, and intel_pasid_free_table() then frees the PASID directory pages, so the IOMMU can keep walking a stale Present=1 entry that points at freed memory. While x86 provides strong write ordering, the compiler may reorder the two 64-bit writes to the entry, and the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes. Commit c1e4f1dccbe9d ("iommu/vt-d: Clear Present bit before tearing down context entry") fixed this exact pattern in domain_context_clear_one() and the copied-context path, but device_pasid_table_teardown() was not converted. Align it with the "Guidance to Software for Invalidations" in the VT-d spec, Section 6.5.3.3, using the same ownership handshake as the sibling fix: clear only the Present bit, flush it to the IOMMU, perform the context-cache invalidation, and only then zero the rest of the entry. The Linux kernel CVE team has assigned CVE-2026-74439 to this issue. Affected and fixed versions =========================== Issue introduced in 6.9 with commit 81e921fd321614c2ad8ac333b041aae1da7a1c6d and fixed in 6.12.97 with commit e9e83bcfe37dc719182500dd823c03ab57d934f0 Issue introduced in 6.9 with commit 81e921fd321614c2ad8ac333b041aae1da7a1c6d and fixed in 6.18.40 with commit 588718101e8449605f1c7e858fecb7cfa701cdab Issue introduced in 6.9 with commit 81e921fd321614c2ad8ac333b041aae1da7a1c6d and fixed in 7.1.5 with commit 7fd4077dc92b91b1b844333c0a06bb9e286db10a Issue introduced in 6.9 with commit 81e921fd321614c2ad8ac333b041aae1da7a1c6d and fixed in 7.2-rc1 with commit f46452c3df7a8d8a5addc0926e76ef19ea7da0a0 Issue introduced in 6.8.2 with commit 333fe86968482ca701c609af590003bcea450e8f 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-2026-74439 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/iommu/intel/pasid.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/e9e83bcfe37dc719182500dd823c03ab57d934f0 https://git.kernel.org/stable/c/588718101e8449605f1c7e858fecb7cfa701cdab https://git.kernel.org/stable/c/7fd4077dc92b91b1b844333c0a06bb9e286db10a https://git.kernel.org/stable/c/f46452c3df7a8d8a5addc0926e76ef19ea7da0a0