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 83441606A33F for ; Thu, 29 Oct 2026 20:43:08 +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=S8FbsmnN Received: by kanga.kvack.org (Postfix) id 9F1D06B05EE; Thu, 29 Oct 2026 16:43:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9C9626B05EF; Thu, 29 Oct 2026 16:43:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8BA2A6B05F0; Thu, 29 Oct 2026 16:43:07 -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 6E9046B05EE for ; Thu, 29 Oct 2026 16:43:07 -0400 (EDT) Received: from smtpin19.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 0D2014036D for ; Thu, 29 Oct 2026 20:43:07 +0000 (UTC) X-FDA: 85376838414.19.C31D3C8 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf12.hostedemail.com (Postfix) with ESMTP id 557E940007 for ; Thu, 29 Oct 2026 20:43:05 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=S8FbsmnN; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf12.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793306585; 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=ukvSnc9VVc3+aKTeb9PBaNc8Py82EOnJibhIoUxMHZg=; b=etfc9/ppjlZvHklOfzCXV89sq+5gwsQRiRYSGteRu2XDt3fXJpAtLUMMfWVREgm2hCF/Ii mpDcO+Q8OPfqIwGM187Vme8bp0OIUhzw5gSLSMLHouC8DLGDnzjup0j2+MGAq7oKsM+YCX JJ9X2U5RxzZZvxg5WaMik1HTPI8bMk4= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=S8FbsmnN; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf12.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793306585; b=gh/A9bmEEdSo7LI5EAqCTSc/Ripl6vzXaMjEEZHjN3VHOvXvcO/wIZl9qvwRDk6LUwT21g Qob0Ges3uHZGVYwwnbwpg+A5ouf861gV5cF8AQc/x7zpbI4wwm7tM/8qMDFBeuIg+UU+/R Wb5mbBZkZu53cG5HFPv87mnsOjw2A4Q= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id D654160619; Thu, 29 Oct 2026 20:43:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33C581F01825; Thu, 29 Oct 2026 20:42:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306584; bh=ukvSnc9VVc3+aKTeb9PBaNc8Py82EOnJibhIoUxMHZg=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=S8FbsmnNOor9iMt8aGi/JafQAxsLqG3RGF67M4+YkY+bfjLhZP05oOL+wLOh/VMVi xpxXBig5h+Ps5h0PkUYh0RJcUSrNmkCMzKTKvGA3HWL0cmQq8nJpI2zsIlgFK+Ewkn ArmeXbYFayYttDT2/E+E2ZIMWAkeIin1CRybodeUgv53L+r3L4Y/JF2GeyH9TEP3qm 2YDBuuePBEA0zf0C6CWmmEfuCvium6jPSQp8dKwzaq1tJGPopigJJ5ztzX9j26W8h5 hyObhrs03z9OqcOuYcHKu40pDkONYhgOFYxRA/kRczyV9HVZ9cND6kv329GCBt7FBf fLADHXyCo7eNA== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:34 +0100 Subject: [PATCH v2 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: <20261029-fixes_core-v2-39-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@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=2216; i=david@kernel.org; h=from:subject:message-id; bh=qFI0e6Gq7RNpgOyDOhV5hfkjLlYbA5wha1P7Baiobyg=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer+1c7zu38PLkvM6G9nsHQlYwtF++tW0rU+Kcoqaub UunCa5Y0VHKwiDGwSArpsgSFHzf4OXLdbXVbnzMMHNYmUCGMHBxCsBEJixjZPjl535bMbTc2Fzh a/PcuJbe6S/9w2XXTLcp5inr/KGxIorhD+entrzndb6N/27ZGRVYrhZjq/X22eYhbnw5LbLLKmo XPwA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 557E940007 X-Stat-Signature: 6xnkj1sag45ebn9aarmet4zgyii6xkqw 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-Rspam-User: X-HE-Tag: 1793306585-94083 X-HE-Meta: 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 VvEHY7Pp j9B20jsabXUncWXzsMDTULQTTW/8G5tlFxNw+v3kiurP1+X/H+OY8LvTnuUROouqAmgiowN3AQ3+Q3II60lR+PTZZvVQUivazG+MIScIyN0G2ctp8RixRgza5sHupYWyZ018ESeMp2NXKuEEZ/z2IU/zKyqsFGIVdqogiXW4hJNSKF2H6YDlA6VZAxBT2koB7tVfejveJHxZsuKuBR4mwigQl+iFR95FLiA7VD2a5QbCC2UoZP4gqiNzQCxasve+YlMO0mG2DD7dx234etzTBbSub7oOfoWo9pNXgJCDfCG0324UXgxPJOR9isAsNvqNigXK9+pDOyGFmKWcdqANOj44TAo39dEcxeRa/Pk4HsN+EKBQypWyiCjGv7aN3bDp0QPLxeEQNUQ2Zp7SIutGUGHSE3b10Wc/l9E2+FyAMWpvy6Awf550Enh1wkw== 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 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 dbfb8f98b189..9c51925825cb 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