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 3AD08606A31F for ; Thu, 29 Oct 2026 20:41:54 +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=hQ+wzstj; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=RGLYR88r DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Cc:To:In-Reply-To:References :Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=zArSmg7yLUQusiUDBjlm/kScYeO/TmH/P9/Smu4iQZg=; b=hQ+wzstj5L5vYy EdpPxM8/V/gtPxLX0G+SDO7aWnoV0QVRx7LyMDQBLFHHML2cVpWi/cM3vp39/8sm/cUmp4DA+oa3c NkByon8wWMm4lqTmfUvBzedLwVfxijjxVGxWkUDWLWGvHBn26xytS4jr8KmyZNQ8OFZIFssiegToS dmzt/l9MBUvRYDYo8/8yx7T6eGwB8L+qV49aiQYDUljiEWhAoTVNes6S5tfyMylA5kN7+bYPMnDgY fJmHgWsY7zPmsoIorgr6/nNQOpGSeL1si58ALsIjtX2VTpawDzwtjjXt6AZLyrb0OGrIAI5+qXv6l tQ0laClIPFuLnZz+xVoA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMWwb-0000000AM55-44l3; Thu, 29 Oct 2026 20:41:53 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMWwa-0000000AM4S-1hgt for kexec@lists.infradead.org; Thu, 29 Oct 2026 20:41:52 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 439D1600DA; Thu, 29 Oct 2026 20:41:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D979D1F01824; Thu, 29 Oct 2026 20:41:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306511; bh=zArSmg7yLUQusiUDBjlm/kScYeO/TmH/P9/Smu4iQZg=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=RGLYR88roEEbDd5tCeYUTOpvVfraAhTmG++35UVmmW+MOOjtMfDoQbZ3JwNu9EYK7 a99vFMdfcGf8o5juAUZnbJ5xZs8mAGQ1+gjvsFf6NHOO3vpEmbqZVt3FCXH1tgKNfy WHJSd4Lz8UjYheY8b6tfHXBpyMyIhevr0bOkLKm7e0YsAY15rmrqUd+JMgpP99OcGM p5rxJpPQrcARGEcSkJF+8J7+1oI/T8LiSMX5XgFh2+E67ydfTgPDCA44s95fCGJaSG Vvv0OX3xJ1ptZi56r/nPn2GsnNt0bERfJYkrF8Yyh5tqVEW86MP0+rqj4DGWD7vADq jNLTFzqpOM9ZQ== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:29 +0100 Subject: [PATCH v2 34/47] mm/madvise: fix data loss from MADV_FREE on a KSM page X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-34-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=1733; i=david@kernel.org; h=from:subject:message-id; bh=K1BVe7ZYRTk2Zt50NT+PN3jE7jOx7NQzRVqTDwh0m6c=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer+04M4X18V1Z9xPSyy/e+WsUa9zSlnOmMjtRcs/1g NZP74686ShlYRDjYJAVU2QJCr5v8PLlutpqNz5mmDmsTCBDGLg4BWAi+dYMf8Ucyw4tm2A0J/OW z8VXDYXdXeKvv2wMrxY7eGn1EVedZ0sY/lmd9HP2W/rCXJN5+ou8mx8EBQO2BC78+WrrK7Gc7rI f+9kB X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" X-Spam-Status: No, score=-18.9 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,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 MADV_FREE can clear the dirty flag of a singly mapped KSM folio. The folio remains in the stable tree and can gain new mappings without being dirtied again. Once marked lazyfree, reclaim can discard data that those mappings still need. KSM always marks a folio dirty when converting it to a KSM folio in try_to_merge_one_page(). Marking a folio lazyfree clears PG_swapbacked but leaves PG_dirty unchanged. Preserving PG_dirty makes reclaim restore PG_swapbacked instead of discarding the folio. This also protects folios that were already lazyfree when KSM converted them. Skip KSM folios before clearing their dirty flag, checking under the folio lock to serialize with KSM conversion. Fixes: 854e9ed09ded ("mm: support madvise(MADV_FREE)") Cc: stable@vger.kernel.org Reported-by: Josef Bacik Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Xu Xin Signed-off-by: David Hildenbrand (Arm) --- mm/madvise.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index 75b409e97dbf..a16e3cb256b7 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -756,6 +756,15 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, if (folio_test_swapcache(folio) || folio_test_dirty(folio)) { if (!folio_trylock(folio)) continue; + /* + * KSM folios can gain new mappings at any time, so we must + * not clear their dirty flag. + */ + if (folio_test_ksm(folio)) { + folio_unlock(folio); + continue; + } + /* * If we have a large folio at this point, we know it is * fully mapped so if its mapcount is the same as its -- 2.43.0