From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id CDFDB606A31A for ; Mon, 26 Oct 2026 23:29:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=GiO4u4AK Received: by kanga.kvack.org (Postfix) id F0D066B05F5; Mon, 26 Oct 2026 19:29:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EE5766B05F6; Mon, 26 Oct 2026 19:29:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DFC396B05F7; Mon, 26 Oct 2026 19:29:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id B6E7B6B05F5 for ; Mon, 26 Oct 2026 19:29:49 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 56C57140181 for ; Mon, 26 Oct 2026 23:29:49 +0000 (UTC) X-FDA: 85366372098.16.B722A23 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf09.hostedemail.com (Postfix) with ESMTP id 8CD54140005 for ; Mon, 26 Oct 2026 23:29:47 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=GiO4u4AK; spf=pass (imf09.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793057387; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=coOQRGDsT+wJUVW51ZA0Qbw+6l1l2M6ICO7oefEeEsg=; b=jEX0LPzsIpEGkI33kWP6WI1uAnhvkjZB5Hz4m9C3OS2xbPNXRxJvmC+htgnYi6JdRBJIbp YNfXvK9IfYnSAs2yB+VTl2dv2T0S9W/LC3uMT7FmOQ4giSuZJ30j/7jpRB6h1JEUYzt++l ABOunLW3i0W1XBRuksY+BP6chZl1DC4= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793057387; b=CikJDSro84kr6NUMGUHoMEtop1zGWxgL5SBD1e2cKLl95LxxgX7iwv93j148WkyZ9D9g3w KbsNih2PaVD/91IA1gmRVrGGR3d8rDltkSqvhPudNQSHLmG54SRrtoXyJebMq3Y2nzkFtj FPM6cYkWR1syFiYa8V12z0Mz3JnnMKE= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=GiO4u4AK; spf=pass (imf09.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C57DB40B83; Mon, 26 Oct 2026 23:29:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 776751F01825; Mon, 26 Oct 2026 23:29:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793057386; bh=coOQRGDsT+wJUVW51ZA0Qbw+6l1l2M6ICO7oefEeEsg=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=GiO4u4AKmDnNc8YPvYmnDQq3BaIr+RptwEAcqRK360IcwrF2iBXGw1J4DWyV4sHLw MSmQi5baxNEw+IWu5HmCurp2H0sINX0XT1PqKiMpshw1F2bnM249lb1mP7hvV3dxpi N+m8PyNfp4nCcfiSAuW26vuJptP/q9S+unB4blp/je/Ms+iGljDFKSrQg9w5cS7geq 1CVPNZZRNDlD5jgns/lYTAziDHZsp0MK3FeSKb4cJb9NqDwRkM1P3hdksaafMGCq6r tMOZBP+r6O5Og0wsloC7zDVaRJvM5uwjDSdXuTuIZRJxrM835hsFQah5qSZ7+y6oUc T4SZkCG4ibHWQ== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:58 +0100 Subject: [PATCH 38/46] mm/ksm: reset the unstable trees of all nodes X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261027-fixes_core-v1-38-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> In-Reply-To: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, Josef Bacik , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2111; i=david@kernel.org; h=from:subject:message-id; bh=FsjPKsNWJYzmMrPhyxtJFP2mccjtdE2o5Mf6O6Ctwdk=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu35/BVZrBpbfEKWi9gCZPyGl1UYv5LxucgjodX84/d nXj1IAzHaUsDGIcDLJiiixBwfcNXr5cV1vtxscMM4eVCWQIAxenAExkcSMjw92qMGGWqxeDpB/t 55ue9/pO5JsfnUq5j/YnlKxvV5Iv38fwv0hX1t79y//MtLXGB8QSL6zP3r7r9IbVn0+8efTB5KH fXW4A X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 8CD54140005 X-Stat-Signature: c43a18neymmb7jyo3dq364ncjzh8ecwu X-Rspam-User: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1793057387-344937 X-HE-Meta: U2FsdGVkX18csBcQyNV02Tmv+A3ERGF/ARR8N5snzRMp1/0CQvizaG7p/IKRDk/B6x8kYMGFV4Tvakukiuee1TXfaP5EcAqYbjPinq6Fu3Fim0eIkK99BX5UzgJfQU6Dv3KUNuhr8G+8d28kNUXD8/ImaDDxVP3NYlvIvwDoz6ccAKqRtlSBdf7ras/OQFubUj/MnFQ1qjuDJV+P0sYFkvcDZhA28xb1Cpz8hzMlx2zv1+TMgPEeha1oDrftlN4vfmZqGXI6HSCIkzFz/K/aniZXVv8G/JGxThgrezUY+B+ySws4d8NLJ6k3RIsj018t89Ps/zKNJTW5Peyxua4rht+gCjI8sy15Brw1cdBU7V7Cdhs6oZM3AwGk2ly0IaHsIKDAhLLj5znf3ejNyNVAFrG2yamwyILaa/8kgZxyAyFwRwRYDebmJ1GY6Sm2KTlEb7GfYgK2J09s2w9gOwGNWeEC7GKYoXHM9YsUuIs5EfnQqxEVfSk2x/ZazUfLfr5zdpfEKtOa8SuNY7rfjQSYzaEWiNbDPuBIBnlkVSyianG4j5/D/PLtJxOScK8LWP7h6woURH7YaBQqrM31bOFuOZ35migTIpcFThKHubQNGnvb0Pz2S0xmeJdU6/anumGZDu8OwRMDUZuNMSeQ2YLajx4NYLlxYbDS/seotb7k0bFz5uE0EAlVnSuiPe7v6Mgo9U/iYsOgT4wEhs4vk4m+bW/12RThfOv+gso6XLiRql0jo9av6u/KT5lOZl/JX5bA9zanlsAbH/w1EPBV33pBaSGXyGP4h5DXmWxSxTNu78sq+BAdfrqNGpnF4U9atuau9ug5IHwiLCU+EiawokQp3pAOg9QYXCwnoewhzsk97vG/rAoKArdZzEgWLrXWiD68Y/Ox004G2YMFuzIHJ04dBLg5Nv87MA4hBugqozPmybq6dkDPv8oDZxpl9pzK21IaLuvruaPq9YGQSNx4M9P MWl+Z67w EKXYtQoA6nFhDZyAWzBpuNLI9WYajDU/SSlDeAN0ND+GSTJ3TyvMCsVxq7JLQIGCPbyYgNpxWzx5zve3fijDLwB5Ue8wQIgsoPZQk36MIBHlnJSjQ0IRBVOWU1rjlZE/Kcm7EmloL7sYiTR7N1Z7jklqVn5MHdcM/JVUhCu5aWpa8AdUzpQyORhNYpT9IJh31iApa9/h6P1H41KPEfEGY1BbqUCZWSm5JAdqJAhWwD5nrWs2hn3L4QxgcBnGXTviAkYzIZG0t77e3/W0a5Cr7ljwqLeP6uWbQLKytEQ9IeYV34LA5xt9gaqy0c7odoYE4IdBvBaXQvttqZwphAxn9bjZQthKaLusSllqRj2QKVv0TDzS8joKo6SqYJrMrDsecGrJq Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Each full scan resets ksm_nr_node_ids unstable tree roots. Enabling merge_across_nodes resets this count to 1, even if per-node roots were previously allocated. So when toggling "merge_across_nodes" 0 -> 1 -> 0, a scan that starts while the setting is 1 and continues after switching back to 0 can encounter stale unstable tree roots, resulting in UAF. Only root is allowed to change "merge_across_nodes", and the documented sequence is: "merge_across_nodes setting can be changed only when there are no ksm shared pages in the system: set run 2 to unmerge pages first, then to 1 after changing merge_across_nodes, to remerge according to the new setting." Let's fix it by tracking in ksm_nr_node_ids the actual number of allocated tree roots. remove_all_stable_nodes() and ksm_check_stable_tree() will now scan more tree roots (skipping the empty ones), which is harmless. Fixes: ef53d16cded7 ("ksm: allocate roots when needed") Cc: stable@vger.kernel.org Reported-by: Josef Bacik Signed-off-by: David Hildenbrand (Arm) --- mm/ksm.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index dbfb8f98b1892..9c51925825cbf 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -475,6 +475,7 @@ static void advisor_stop_scan(void) #ifdef CONFIG_NUMA /* Zeroed when merging across nodes is not allowed */ static unsigned int ksm_merge_across_nodes = 1; +/* Number of allocated stable and unstable tree roots. */ static int ksm_nr_node_ids = 1; #else #define ksm_merge_across_nodes 1U @@ -3636,14 +3637,13 @@ static ssize_t merge_across_nodes_store(struct kobject *kobj, else { root_stable_tree = buf; root_unstable_tree = buf + nr_node_ids; + ksm_nr_node_ids = nr_node_ids; /* Stable tree is empty but not the unstable */ root_unstable_tree[0] = one_unstable_tree[0]; } } - if (!err) { + if (!err) ksm_merge_across_nodes = knob; - ksm_nr_node_ids = knob ? 1 : nr_node_ids; - } } mutex_unlock(&ksm_thread_mutex); -- 2.43.0