From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2970B3F0AB3 for ; Fri, 8 May 2026 14:26:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778250397; cv=none; b=j3Z+A3DAmS+/eOzBiMzJy9G8JLqsQoOwrhtG+vjQc/Q/d9NdKaK8CbC7zVy/M+ZD666diY1eSo8T8BK3Di0CG2ffkyn3XfgFy/S02778hJxoXpDnUQHKH+kkUtrau1Hn9dJ7yXQjKDkh4bmK+nsaZwnoK9wovQ9PKdXRUBBqIq8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778250397; c=relaxed/simple; bh=lcUD193Ucnj7tVOfz8QWsUkSVn9iL8JvmGDACp/EcFo=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=GNFtIKbIdxfVYP6UxnO8+iuDQ5TBQ7zjyzSKSTD/0JUignw6fgaH3v45QmRiY29wQ2PlIUjDw5ApXWgEvbif17lcSTmN+DHlg/6eOEcKqvjdcPDngu3twu0gOpv65qaZKzJ/+Kqf8Zx/dNukELPvRYUAxCVN9OAM7qhABG5KyqU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=N9L+acP8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="N9L+acP8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AC219C2BCB0; Fri, 8 May 2026 14:26:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778250397; bh=lcUD193Ucnj7tVOfz8QWsUkSVn9iL8JvmGDACp/EcFo=; h=From:To:Cc:Subject:Date:Reply-To:From; b=N9L+acP8+W/9rnKeTNQmiEpMsJ0DXvkDNmk9OyJ1mM9GeQRXr5jKuzKqa3bA7uTQM 7FejTk8zz1d9FlGQtapFyeuBxbHuLSE31NhBE7mEa/8PJ9sVeTOC1XHgv3/p760VHT HqgNU6J2tsSO8j2Xjx64VlxLs4lMyjNguJrd4trc= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-43417: sched/mmcid: Handle vfork()/CLONE_VM correctly Date: Fri, 8 May 2026 16:22:26 +0200 Message-ID: <2026050845-CVE-2026-43417-e9af@gregkh> X-Mailer: git-send-email 2.54.0 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=2564; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=gapfg3P6egXAAbuObwrQNghbufHDzA/LuP3QSTS+zFI=; b=owGbwMvMwCRo6H6F97bub03G02pJDJl/P1Zd0cpZ/N+7/MtK/8zFfx5fSN15V/NQm16c/f4zF +MnXTAw6ohlYRBkYpAVU2T5so3n6P6KQ4pehranYeawMoEMYeDiFICJHP7KMItZcvlPbcMr7X7r Cw5MfndiVqtWkgzDgpNqsRnfJmwUn/W389zqo6en6D3zbgMA 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: sched/mmcid: Handle vfork()/CLONE_VM correctly Matthieu and Jiri reported stalls where a task endlessly loops in mm_get_cid() when scheduling in. It turned out that the logic which handles vfork()'ed tasks is broken. It is invoked when the number of tasks associated to a process is smaller than the number of MMCID users. It then walks the task list to find the vfork()'ed task, but accounts all the already processed tasks as well. If that double processing brings the number of to be handled tasks to 0, the walk stops and the vfork()'ed task's CID is not fixed up. As a consequence a subsequent schedule in fails to acquire a (transitional) CID and the machine stalls. Cure this by removing the accounting condition and make the fixup always walk the full task list if it could not find the exact number of users in the process' thread list. The Linux kernel CVE team has assigned CVE-2026-43417 to this issue. Affected and fixed versions =========================== Issue introduced in 6.19 with commit fbd0e71dc370af73f6b316e4de9eed273dd90340 and fixed in 6.19.9 with commit e6761cdce78a8919a537989afb6aaf6881469f83 Issue introduced in 6.19 with commit fbd0e71dc370af73f6b316e4de9eed273dd90340 and fixed in 7.0 with commit 28b5a1395036d6c7a6c8034d85ad3d7d365f192c 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-2026-43417 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: kernel/sched/core.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/e6761cdce78a8919a537989afb6aaf6881469f83 https://git.kernel.org/stable/c/28b5a1395036d6c7a6c8034d85ad3d7d365f192c