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 D3348606A321 for ; Mon, 26 Oct 2026 23:28:15 +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=a1SAmhI7; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=a2oBtA1M 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=MsPh/eggStrjiHwP9EayEEqNGoFUTjhuNZcTRbaJqvA=; b=a1SAmhI7oOKAyC A6MT6hnKbXiKpiy1oAe8ml6bEqynEP/1OvwzEeQ4udoEU1A5qYHfAkY4Zy/HMTFYclVSPNubaWLTO 6vH5S8p4W5B88SC6y2VAIzdMqkMkV+o6i9M5hAKJ1ByCSXT4l7tq3iVs6e9Xc1i0HAZGZkzPekaNp 2x47dsQaRBbcsvZA+EhsIBgjGcgker9YZ0c60RzOAWYizP2MIQNecmQfn4BGggFGXt9WMWOqOHnAN HwafZuYprYrmKocohvaxAPW79Avr0uuNB0OM3H5fD2z5AU4jPwv6Zv3pIw4HjC041oOk+/vbiLMwl 9Sn5PqaGk3BvB1cujHqg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLU6x-00000003RE4-2LeS; Mon, 26 Oct 2026 23:28:15 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLU6w-00000003RDx-1yYG for kexec@lists.infradead.org; Mon, 26 Oct 2026 23:28:14 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 1FE2041FF9; Mon, 26 Oct 2026 23:28:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07B5F1F031E8; Mon, 26 Oct 2026 23:27:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793057294; bh=MsPh/eggStrjiHwP9EayEEqNGoFUTjhuNZcTRbaJqvA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=a2oBtA1MZUa66kHRki/kVGEs4Zx8bYN/Yl5uKbWs9K/ii8a0kAHkMnSDLIdapPOWX tT9/m5gFYOUnJ0bxIPU3CBuADzf8viUbnqgkZg+qgxV89v2GUDN4AHW0Z1wAHkcduk PIxQdnRdZJHbXvgTH5eaPIsMoZPvrYBYhtl/jAi8ljDXzIVG1kAItasz/VnHm/ks1x Iuz1X6uJ7GLX4jmLwHxR9GyQb3CUrqzCsMYq+8T3s2R5uK7EIuMRjtCCGsaXSkwqoJ fIyFLJR3wL5Y6vXz+2Okd6zBZ1WqzzuUzJB6PvOkZKTgLrcpSfx84MZ2uDvQrjryH6 7UK0jOt7OUuWw== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:53 +0100 Subject: [PATCH 33/46] 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: <20261027-fixes_core-v1-33-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> In-Reply-To: <20261027-fixes_core-v1-0-6f74bec9a5bb@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=1695; i=david@kernel.org; h=from:subject:message-id; bh=qp+B7fki+e2EPAcFDpqxiM3FT4Otm8jPFLB5fTfcqqc=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu35++XlaKOa1L9OCCE0uzuD4K1eSJ2TXlGKhMad/5+ 7MYb/7rjlIWBjEOBlkxRZag4PsGL1+uq61242OGmcPKBDKEgYtTACYS9Z3hf4lNQMf/pQy/qw6c fx1krnTVIfBoMcfe/NDGiKW8PNPauRgZLuTsfCHh5j9fZiH/fc/r4R9ag06c/lFl0HhBN2Pn7x3 2/AA= 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=-19.2 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,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) 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 75b409e97dbf2..a16e3cb256b7b 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