From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 5E7B5606A33B for ; Thu, 29 Oct 2026 20:41:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TE1y0ZbL Received: by kanga.kvack.org (Postfix) id 4E5166B05E0; Thu, 29 Oct 2026 16:41:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4BC516B05E1; Thu, 29 Oct 2026 16:41:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3AC116B05E2; Thu, 29 Oct 2026 16:41:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 14AC86B05E0 for ; Thu, 29 Oct 2026 16:41:10 -0400 (EDT) Received: from smtpin15.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 993631C3BF6 for ; Thu, 29 Oct 2026 20:41:09 +0000 (UTC) X-FDA: 85376833458.15.169DE33 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf27.hostedemail.com (Postfix) with ESMTP id EC2A440003 for ; Thu, 29 Oct 2026 20:41:07 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=TE1y0ZbL; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793306467; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=zTwOe2rhygBTqbimADjsD30DCMGB2E0StBtyrsEknSA=; b=N6ynI+QsD7uJXLmPBGS92x31+/SeOPYAV46gnG40Kx57Cli8g/14raKO1slMUMRGhZJ/N9 8P5/x6ELuVUpz/wi0xVlrl9fskuLMaMs3cOKdTX3EDsjiT0Jcy10IO/18aKXwY2RYI9ZZj kMyyelpMNVBYfQtj2oz52oNGWl8n+tA= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=TE1y0ZbL; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793306467; b=iOfkDMijRlr4teA9WYrFnbU6hHrFuE/6vLdbCAHtF1k3njx6t4KrHTRlwzDZkhMqOf92Wz RuZt3cRvIvL4qfUaaB/ZQohDj9N5KikbQgjEfoaKD1M3FSLMJDNKu519bgQzpwGZq7RadS 8Fxk5oIBIi4v+CQ0qqmM8rZ5swJnLZ0= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 7B3516062C; Thu, 29 Oct 2026 20:41:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 265891F01816; Thu, 29 Oct 2026 20:40:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306467; bh=zTwOe2rhygBTqbimADjsD30DCMGB2E0StBtyrsEknSA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=TE1y0ZbL3VVf4eb0u189422pKiAjJR66N2I9oRbQQKW9568wfoomQtdaN6haewvQ/ QvLKMTWJGEIpLmu872vicnNj8EMylIE6cimSkE7cVVxhve4jg0GGIRmlhdB4EW+Rfs bx4v2727E0rc3ijNbosG45F77CfN2c9fJw31CpRuioX3BtcKRyuofi5KCM412z8Yis b+xHStb8Zv+yfOsQ8t+1K8J/VWSvKbzlyPs3a1VrzphHv9cZ7fI88mgneYvJjxzOHJ v8ViB9WkGVew7svI82MfmrAzh9Hrk1i0lS0t6SRranladPVqdFUN08fQx4ZQ8MBeuv AEoxd+/ch8j5g== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:26 +0100 Subject: [PATCH v2 31/47] mm/mremap: recheck PUDs under the page table lock X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-31-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, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2380; i=david@kernel.org; h=from:subject:message-id; bh=+B9w/NrDyjyp/nHRZsfFIxa7vmKtKobl06e6HnkArmM=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer+24/V3GfMO74vTaKbNNWy5eXLrUfJ6mT+ijWK8PH W4s/RsTO0pZGMQ4GGTFFFmCgu8bvHy5rrbajY8ZZg4rE8gQBi5OAZiIXx3D/zzBwL2X6+arx9qJ nJHpi56T+PWSp2qJUN7ShvrtW9ett2H4HzPRY6fWRadVIoXiKeVO3i4zbr8QeZnw4P6WpzOSJZS leQA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Queue-Id: EC2A440003 X-Rspam-User: X-Stat-Signature: 1scipq854xw7kj38i1i3ncdca8f3z3zs X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam03 X-HE-Tag: 1793306467-710882 X-HE-Meta: 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 QwYepaGH qFBHqK5t/aHX6+aXuTvusAkKsoWEuSZ0EBqEo53Xl/ddlF+XGmtGf3g8Ti2lG7LTQsolE6vgl2+ADwCjCnekfHwxCadhhX9Z6xmFNSL/5PfoIMpc7BkkmP+3UDfb5YoBBAkXk1Z22PwTavt3dRM6K/+7rzVYlwDG8YGNZ5aSDFFyQHVh1qoMdOm/xd6dgpNWBKvF4BpF+1epBLta+kf2/bjCFaoAqvtnVJTlxEDdTycOZYDLVv8hxuJSS1vxkYSP7Ux1RLtEd142fS/7nEnDOtFsWHdXaWHnLg3LZrlT9soKYuGtojpRGvnUWt/JvW9ZqGe7Z Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Once get_old_pud() is fixed to accept PUD leaves, unmap_mapping_range() can clear a leaf between the lookup and the move. Holding mmap_lock in write mode does not prevent this. If the zap happens before move_page_tables() tests the entry, an empty PUD can reach move_normal_pud(), where pud_populate() turns it into a present page table entry. If it happens after the test, move_huge_pud() can instead try to move an empty entry, triggering CONFIG_DEBUG_VM warnings on powerpc. Recheck the source under the page table lock in both helpers. Treat an empty source in move_normal_pud() as a completed move, and use __pud_trans_huge_lock() in move_huge_pud(). In the future we should likely have the code lookup a PUD/PMD lockless once, instead of multiple times, because one of the problematic bits here is the: pud_trans_huge(*old_pud) Fixes: 0881ace292b6 ("mm/mremap: use pmd/pud_poplulate to update page table entries") Cc: stable@vger.kernel.org Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Pedro Falcato Signed-off-by: David Hildenbrand (Arm) --- mm/mremap.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index 16e736c72d9c..91f0865f6aee 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -461,14 +461,18 @@ static bool move_normal_pud(struct pagetable_move_control *pmc, if (new_ptl != old_ptl) spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); - /* Clear the pud */ pud = *old_pud; + if (unlikely(pud_none(pud))) + goto out_unlock; + + /* Clear the pud */ pud_clear(old_pud); VM_BUG_ON(!pud_none(*new_pud)); pud_populate(mm, new_pud, pud_pgtable(pud)); flush_tlb_range(vma, pmc->old_addr, pmc->old_addr + PUD_SIZE); +out_unlock: if (new_ptl != old_ptl) spin_unlock(new_ptl); spin_unlock(old_ptl); @@ -503,7 +507,9 @@ static bool move_huge_pud(struct pagetable_move_control *pmc, * We don't have to worry about the ordering of src and dst * ptlocks because exclusive mmap_lock prevents deadlock. */ - old_ptl = pud_lock(mm, old_pud); + old_ptl = __pud_trans_huge_lock(old_pud, vma); + if (unlikely(!old_ptl)) + return false; new_ptl = pud_lockptr(mm, new_pud); if (new_ptl != old_ptl) spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); -- 2.43.0