From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0F578606A31A for ; Tue, 27 Oct 2026 00:14:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=WWMwwWKG; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=X7SMplnL DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Reply-To:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Date: Content-Transfer-Encoding:Content-Type:References:In-Reply-To:Cc:To:Subject: From:Message-ID:MIME-Version:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Unsubscribe-Post:List-Owner; bh=w68zYkQOy3WmZccxDgV99fq/k2lUTuWnaa1zclXv+/I=; b=WWMwwWKGqzaQyXonyD7EHs7LfD 40jFdguePZx1h3D05EiyNE8Vyyj/Mt/7fbXzdbW29ulZRiEoLNgWf14Zsv78AosgAu+6RltngP8gm +8TisOrDoTGD8+Cxu6M9rl1H8FyKxNUFFcYzB/vaH5KEfaCEU163grPYPnQYstylKt3HnBud1gcJZ MDxITI+4xovs2wBdFvTgMAjLdANdy7jZyOiOhS4Km9wgX+kpuj0Jo1YxAyJP/SOSRNLfQeB5cE5ce WmabzSjnfJvWsr9M9vZCT2bNIKgsokCsRZF0d6v55f1t+X8CjhX4YyUnkr+Jgx/cnxrbJiiMw8fDy NSGCL2Kg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLUpM-00000003W44-2ufs; Tue, 27 Oct 2026 00:14:08 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLUpL-00000003W2u-1ffk for kexec@lists.infradead.org; Tue, 27 Oct 2026 00:14:07 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id CF4F660213; Tue, 27 Oct 2026 00:14:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 047C31F01825; Tue, 27 Oct 2026 00:14:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793060046; bh=w68zYkQOy3WmZccxDgV99fq/k2lUTuWnaa1zclXv+/I=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=X7SMplnLDLNHa4l4dX2hqT1DVrjwCz1df4DTrOW13XR/5ocBpim7Wx63gsomsE6cE gbGhxLu2RO1dnHkJeI+Eqm2msYvY8KBEq+Beuwn3TqUET3Hq8R29hGVpktLiR4dJhJ P0t/Pc+GgSunsTjhhdQvF6DhapG+do/k8qwoAX6ng0cP3QeySyZAZpc5+Crzpv/2t7 AsOTe5qYD2G2bzlbncPYcpkWPltuOaSvb+2BX7zrzPwuAw9Ly+6MQPvCGdPBTmIicg HDlfZ15pghThMUKYGtJ5pytF5GLrK234dEF6yH+7yrpo2ReCVuHmmxNqqvOzwseEjh iMHpZgydtGSIQ== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 38/46] mm/ksm: reset the unstable trees of all nodes To: =?utf-8?b?RGF2aWQgSGlsZGVuYnJhbmQgKEFybSk=?= , "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" , =?utf-8?b?TWF0dGhldyBXaWxjb3ggKE9yYWNsZSk=?= , "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: kexec@lists.infradead.org, "Josef Bacik" In-Reply-To: <20261027-fixes_core-v1-38-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-38-6f74bec9a5bb@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 27 Oct 2026 00:14:03 +0000 X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "kexec" X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: > 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. >=20 > 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. >=20 > 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." >=20 > Let's fix it by tracking in ksm_nr_node_ids the actual number of > allocated tree roots. >=20 > remove_all_stable_nodes() and ksm_check_stable_tree() will now scan > more tree roots (skipping the empty ones), which is harmless. >=20 > Fixes: ef53d16cded7 ("ksm: allocate roots when needed") > Cc: stable@vger.kernel.org > Reported-by: Josef Bacik > Signed-off-by: David Hildenbrand (Arm) Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261027-fixes_core= -v1-0-6f74bec9a5bb@kernel.org?part=3D38