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 5EBFD606A331 for ; Tue, 27 Oct 2026 00:13:48 +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=SgYkwXv2; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=W/CP9SX4 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=2vnlERlJNAFOuSRlH/67bOAJMpNP9jaP45wQMRMKEqU=; b=SgYkwXv2R0OlaCbRS1Md/MFiNH ZZVV7dSZm3nv9v1mf1VC1p04sxG/ogeB0q8Xt+s3rJK04bX05IUGlnM1ai4VkhKPBYbjF4T9Dmzi3 i23tU4Z1mAiYGr3kgJZihSoSffl+H8F9OI3uK4tDDi+dHVaUALfOpzuFHqGC7YkIiTTx38+Ho66g7 2mKgRNJPduufy6UnO3z3+DizZThD6PihBUmaKz2PYML3OjkFepbQFs+q7VG1gVpCiRgvXD8ZyiN1m UeqI2t0KvUt+kRHm3Fm5SLVM197lourml9+S88MKJ02Kf8FCWdYrQd83Npv4dxLRbqQgn+sf6AH/y RchzQ9+A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLUp2-00000003VoM-0MUr; Tue, 27 Oct 2026 00:13:48 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLUp1-00000003Vnt-2OzG for kexec@lists.infradead.org; Tue, 27 Oct 2026 00:13:47 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 5490243657; Tue, 27 Oct 2026 00:13:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2511F1F01825; Tue, 27 Oct 2026 00:13:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793060027; bh=2vnlERlJNAFOuSRlH/67bOAJMpNP9jaP45wQMRMKEqU=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=W/CP9SX4jCxpllSGBUQKl0e1EF7cj4lnIeAHLK5SrPj6tgYh6piKwcnXqqAMBw6a8 1jeFWvBa4avHWrfNLknj+cFpO/1usdt6U2W6WnYiuuj/3WVPyilfRcbtXXRooTbJGd FSRrJKdRhcLDtO0x9usWgfSFSOEY86qnxP9JBdHc1kLkTLSE3Al9MSY3AMqkLBzYet vBym5dgDVXRL73L3AGqpwXkl/LQCHvdwYFcwGVveCAsYJXpxp/CHlOGA+KJj5bydcB 14fA0ZiuciLFGtO5I3BsYOUP4fFyfSoi71TKtWB/P55GjGESmtz8psMwca4tkg2b0O gPmUv2RMNrxkw== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 32/46] mm/memory_hotplug: avoid races in pfn_to_online_page() with dying pgmap 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-v1-32-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-32-6f74bec9a5bb@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 27 Oct 2026 00:13:43 +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_PASS,T_SPF_HELO_TEMPERROR 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: > From: Josef Bacik >=20 > If ZONE_DEVICE memory shares a memory section with ordinary memory, the > section is online and the pfns of the device are valid. > pfn_to_online_page() tells them apart by asking get_dev_pagemap() whether > the pfn belongs to a dev_pagemap. >=20 > get_dev_pagemap() only returns a dev_pagemap whose reference is alive. > memunmap_pages() kills the reference first, waits until all pages are > idle, and then removes the memmap. During all that time the function > finds nothing, and pfn_to_online_page() hands out the struct pages of the > device as if they were online memory. A pfn walker reads them while they > are poisoned and freed. >=20 > The entry in pgmap_array is only deleted after the pages have been > removed. Look at that instead of trying to get a reference. >=20 > This is probably not worth CCing stable. >=20 > Fix generated by an LLM and sent by Josef Bacik in private. >=20 > Fixes: 1f90a3477df3 ("mm: teach pfn_to_online_page() about ZONE_DEVICE se= ction collisions") > Signed-off-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=3D32