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 476CE606A31E for ; Sat, 31 Oct 2026 09:50:28 +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=D55mz271 Received: by kanga.kvack.org (Postfix) id 586F56B05EB; Sat, 31 Oct 2026 05:50:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 536566B05EC; Sat, 31 Oct 2026 05:50:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 425EB6B05ED; Sat, 31 Oct 2026 05:50:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 1367D6B05EB for ; Sat, 31 Oct 2026 05:50:26 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 8ABED40955 for ; Sat, 31 Oct 2026 09:50:26 +0000 (UTC) X-FDA: 85382451252.10.F80AC72 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf25.hostedemail.com (Postfix) with ESMTP id BB44BA0005 for ; Sat, 31 Oct 2026 09:50:24 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=D55mz271; spf=pass (imf25.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-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793440224; b=nmW0BugdRyjdOvzVBXbrnL00X9c60GB6xOvE5v7QndBvkNvz095rnDQHhDuVxF7DcseE3T TD2yrZeB1WpGvEmEgSKar8rp3vUPnyEirlhwhmQ7FyTSU1Qd4L8G3kDWBJLCIR36gqcVoj Z4b09Sfp0zVy99ZcoDjKaRDRBKulfDM= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=D55mz271; spf=pass (imf25.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=1793440224; 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=a7XJnsrw1a5gmHitwDTAR/cnJ4FEA4vxklFTb+Y9pAI=; b=sv/66eje3+YdX4VD+iYbSDGO1pJFyYxLhWQ9RKqocbsM2w1k+rKQbb6cairg2/yOfBj1Kr oGgFLVAwx3EgJPkEslSi4uuwENScZsZuTi91uIkUENfjOVMRGXvImjVfNUsE7BYksf0tyh sPeBwI4chEEgr5fBQSneW7IeiOwHUC0= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 01EEB40E06; Sat, 31 Oct 2026 09:50:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EB23E1F000C1; Sat, 31 Oct 2026 09:50:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793440223; bh=a7XJnsrw1a5gmHitwDTAR/cnJ4FEA4vxklFTb+Y9pAI=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=D55mz271223NPR/LC1mWZwbXNt7+1AppD98IF3Xlhmsw7cr59Bv8ph/Qx9T9wBTnt IRwJ7seKAp3Xt9M0DCeWAyLI/MBriK9GHaWUguJRzUqEOo+TiWgX1qd5uRZCu44wc3 amVr5MQIuUPQd/aX+pFw1+Aqa6T0sOTHCCeSMgSu05Km1pYzwKn2nx9VLksIuSqedo anriGwlarij1k2nk9IYxr5TA0xhzc7DIcNVboZ7ylnFEKgBq+ljyKATpFJ08imOsjt luKTD8IrLdDRCGXQ76EvNimb8cuzICBrv/G7y1QJwDUhW0eiLn4XandQmIWO1ShaKU YWQzaO32/jcow== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:40:08 +0100 Subject: [PATCH v3 39/47] 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: <20261031-fixes_core-v3-39-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@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 , Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2273; i=david@kernel.org; h=from:subject:message-id; bh=nUvclxTiUv/Tum9+/Zt09Qv8koZgF+ihTZzvWN6IkJ0=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebs8SFbm2as8ZL5Oti3XlL6p6yF24d96eSeSMwCaJw rLk7vlRHaUsDGIcDLJiiixBwfcNXr5cV1vtxscMM4eVCWQIAxenAEykZB/D/7A7eX6mD/nX/Ltk 832B+LYAgVaxGd9nsTU7uyRtnjjXYQvDP9WEP9ebK1m+eVvpxFrq87b9VOuZltIVvGG+efeHM0U fGAA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Stat-Signature: ijtj93e4s9s3goh3m51n185qfa9b3hmq X-Spam-Status: No, score=-18.8 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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BB44BA0005 X-Rspam-User: X-HE-Tag: 1793440224-593088 X-HE-Meta: U2FsdGVkX1/JSFzDMiBIXoGK6+/EnADw1LDBsmYnt6WpzqO1js+5+GOSJ+ezo5unlPmuXX2bHplm8BXS3xG5GbJA7oAsHRNuETx7HArge6AjMaUWSyzx+I3iNQTUU1jp6PPyPzaFjl3AKvRnQ+wMjoNGi3kxOvP1BZ3iak3VBjnFPm1pXUWJfC7v6RtHt8bbwFbtABchJeKauXZniYcY1lycLxIusgf58+5vSo8vORGGuYmT7FtRVfBj2JPRW5dWaZfmfOTR/ihdGzAAZD/FFL52CJ4mF9BtocVviMoJxvLP7xnpGljloAUcfAWetHdxUK84yw3fCv64RzhSJ3D2Ynmu1WBaIRl6KonoHb+c68YXKvuzABJyxXcAOgjel/ZhEqd4TNZv096Cdj9qVy/7kmrKYf1LbsMDmzWiQSEqGDoiL85/TlOP1L0vy1dTo/XRqOCkQwWE+/fpJrIe3JaRKb/qxYkDLu3br6jtVdhztndjRoqtemuqkdWS5JsEWWkR2shnNWCizIPshHcdf+P1BLw8YiGZvtmVazswSJanilAGbgHEValuXDiUjRG5qAAgKmTdgj+jkrOiCMmm1MTaUQ5oOglZnal7fnA8GyLfSBJvQ8GaBe2yqVbJa4vDuF0spfHch/RAIxEkAnwnnJR0BdzvdTzzh/RLDqXtQjJ96VZyNJyK/M1KdTaxxS26XX9NXakKAr+FhGxjwitUNNS8IuYiT7VouKugafM+Lbc6VqkwkvMJpOK+yzfDrXQFTqtcO5qnvZpNLB7d8U8RclpaNOVg4Zq9EPoL1Fn8g/KWWdfZPi+p0HLLzY19fI3QaGi2QcN39uLV+PSVPWlwuy8dbR6esuRB6eayg5GsfljDj2ZvSCWQW2X3SEcK7U7lIHCA1+2k9z+t+Jryshe/doROaVKPJJgMS3+QjZPy6Ik7uc0B78u/GNSBgHNBdZSeP7NuLWdu6CIrQmCp5c6zgmy 80Yc4wZs 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 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 Acked-by: Lorenzo Stoakes (ARM) Reviewed-by: Pasha Tatashin Tested-by: Muhammad Usama Anjum 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