From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590417; b=2W3Ptrj2cpxm65+JC2Lkk9B8ca/lOajw2R7Mnf3P6P2i89jmlGr60EdLfOU7p7CJEmm7 u2Kzzw3sIzrWRMB5tXodiaXWppypBkpc/5KUIkAYLnjXa4INdWctxijscYbhG5blNtA9D kPQZf4/jQP8M+9dalK9R3rfy6R5X0mAyvPhUf8ZMwC/nfSqnj3ouXEaDSlOsuon+PKkNn 0UcyT3hlKIzIuXJhXLyBhAolDiC5DyEkvkf+16lgi8AS5fptZAIC+3hY6CjwZMyD36lrW ws1Q6Av6GgojX/4Li79xJiVTHUFKVUCN5WrdN5FKBa+GzIBNWVaYspBfVFXXyzIF0Kg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590417; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=zMzMV9SFelv8CAx1J2Jxv49YAmYsLS2jzEFVbokSxAQ=; b=BrPuQYSgF+pVrSFGG8EeUmJcPEimKu/LXYQWXkHOyIUDuLzPD+ptNfcmoSBEzQxoAdH7 vd2iq8o5JO/yAQr9DJtFV9PqJ8R7K5f0yBwpjnESADP1lEuGa2gELwU4sw8GdZjZcgsZ8 qe/qN5xZKp4oqhPd8J5xRGsbBcLbRCxj3F5cD0Jd6ao7SC0XB17kF9rfIddy9b20WBi22 LoMOZ+Ze/lE+IkcAqJR8dZ91SME7NjmZ8l7qWtAvk5w/1/DxNaO9GfgRxrNi+BCpiRvs+ 15RbbQShdFdWrEi6h0mca0SQ9B9ZeuWickUEEKB3aRwRM3uGuzdaxIc/Ya2ZEpGa70A== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=gsUkbULh; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E9D2E606A8A2; Fri, 13 Nov 2026 17:20:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=gsUkbULh Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BD571F000C4; Fri, 13 Nov 2026 17:20:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590416; bh=zMzMV9SFelv8CAx1J2Jxv49YAmYsLS2jzEFVbokSxAQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gsUkbULhYa0cg57Kah1kxv3JADmVprpyxVYF2uc7bZt8lGlhbxe97vihB+VHFtzGT q+NEbLtVrgmWKHDSeqluCS5hhJDIPN4hKj2+h43oOgJtpqZ/eczi9XIH7dAM+MabA5 iNGxxdEHczt1OFssLL/kVEpECcaScYSAokxUQoh8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josef Bacik , "Lorenzo Stoakes (ARM)" , Xu Xin , Muhammad Usama Anjum , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 6.18 382/686] mm/madvise: fix data loss from MADV_FREE on a KSM page Date: Fri, 13 Nov 2026 10:48:35 -0500 Message-ID: <20261113153833.883949829@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Hildenbrand (Arm) [ Upstream commit 22d043c1da48d6c7274f9dd900714b6d58b7b9c6 ] 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 Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-34-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- mm/madvise.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index 729d8f2f07fd8..bd0a5093a2df2 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -755,6 +755,15 @@ 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 -- 2.53.0