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 B4466606A323 for ; Tue, 27 Oct 2026 03:05:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=c65rOCZf Received: by kanga.kvack.org (Postfix) id A18096B05B7; Mon, 26 Oct 2026 23:05:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9C84E6B05C5; Mon, 26 Oct 2026 23:05:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8B73B6B05D3; Mon, 26 Oct 2026 23:05:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 675476B05B7 for ; Mon, 26 Oct 2026 23:05:37 -0400 (EDT) Received: from smtpin06.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id F0A311208EB for ; Tue, 27 Oct 2026 03:05:36 +0000 (UTC) X-FDA: 85366915872.06.FE3600D Received: from mta1.migadu.com (out-149.mta1.migadu.com [95.215.58.149]) by imf18.hostedemail.com (Postfix) with ESMTP id 5D8451C0002 for ; Tue, 27 Oct 2026 03:05:33 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=c65rOCZf; spf=pass (imf18.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.149 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793070335; 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=S2fYp0D+kux7GkOrzGv4DxJUQ1pHehCh6wWsm9VP8mw=; b=nrrXAlFrXLNTxcng5rKOqWpdLmbgUxNTgf0LNHCTCSbHqu+PUt6UHVhCWJY0lUv/gIX0tv rFXorxXIfE1MpULCwupNT2GN+oIs+kEUch4rb5rWnhyi2zgmCNJKu2dmjbZhDvxAYzI3vN iwQ9f8QZrAV+j/5Q13hoRlbHTE1RBZ4= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=c65rOCZf; spf=pass (imf18.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.149 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793070335; b=mQQvk8QO6iBKNONVCV9fZAANHLklnK+z1wFlV4VxKOmr5s1i6x/yoY3peWSVT4Vl2fIyHs OkcZcTEUKzcHr9hff8ufGFaUsIa/3d6b3bbo4ItWvV5miY/IIIS+do9dLldiJUfnthInFA AekZrVRG/WvTBFt7IaTKlmqpF4cNsIc= X-Envelope-To: linux-mm@kvack.org DKIM-Signature: a=rsa-sha256; bh=PpgTbepyGCQbdry0Tl9jwBnnjb4CaWXJ3ss5elRPGCc=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793070330; v=1; x=1793675130; b=c65rOCZf1Vlq0GQPAQmQqm5wf83ltLhRtUxYonNAqk4jRy4mWveQ6FYHE0z2KgSx0vBBuhwh I5BSaMM8kbNm5zMj9kh6fIQDiuHKd5Weox4bLMD3rtVDFQIbo7eTm65U5091811U3kGr9K6AGAx 2ioEyZte5hznqL0+wFow5F8A= X-Envelope-To: linux-mm@kvack.org Received: by smtp.migadu.com with ESMTPS id 9170fb527649b4ac; Tue, 27 Oct 2026 03:05:20 +0000 X-Mizu-Trace-ID: 9170fb527649b4ac X-Migadu-Flow: FLOW_OUT Message-ID: <62dfb28c-1078-440e-ba23-9068f4958570@linux.dev> Date: Tue, 27 Oct 2026 11:05:01 +0800 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/46] mm/mglru: don't use stack pointers when walking PUD and PMD tables To: "David Hildenbrand (Arm)" , Andrew Morton , Johannes Weiner , Michal Hocko , 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, Josef Bacik , stable@vger.kernel.org References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-1-6f74bec9a5bb@kernel.org> From: Qi Zheng In-Reply-To: <20261027-fixes_core-v1-1-6f74bec9a5bb@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5D8451C0002 X-Stat-Signature: juumxzgin68h8zq1ojzhu6b75hxo1uwx X-Rspam-User: X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,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_SANE_1 autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1793070333-259194 X-HE-Meta: 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 SckppSdc y0QwJsCEbT6SKi6G65/hfkionws53QqR0rDpyc2O+RksYT7tz+2B2Y2tMt4xjy5egFWpivu/K5P2JGF5hpiq+UP+RT+wQGcIXe1/Zv5mDKvxHH6CZ/FgrPSfbAtKbVh//FfweyaEd7IgcIdzdExIEIwm8QI+t9nImUFlb9SpmQkK4f+asBLG6mznVQm0PqCBE7nmrhQjv5tXSLJwMkTOpLl36fhb2csCO4HB0kbcAdClfu88igoOnLUSP8dJDLJzcxqmeugh5WbYyw6H1Cv5ImKzDFb1olAxYwV03arsk5FdOz03uRi3zVmqEWnvXAwMSCjPseuHzKgaQ5v7mX7KTl+EC4GpCtENjJ7vO4aoyhBWvJfhk6aOccuHobdzc93B2TqJKRkRaQSf9qK8qBtELhayRl2y0i/laxES11yhPw4VzU/ZGTIGQ2T5h3Q== 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 On 10/27/26 7:17 AM, David Hildenbrand (Arm) wrote: > From: Josef Bacik > > MGLRU passes stack copies of page-table entries in walk_pud_range() and > walk_pmd_range() when walking to the next level. These copies can become > stale when khugepaged or MADV_DONTNEED (CONFIG_PT_RECLAIM) removes a PTE > table concurrently. > > This pattern dates back to commit bd74fdaea146 ("mm: multi-gen LRU: > support page table walks"). Likely, earlier locking masked the latent > bug. Later changes exposed it: commit 1d65b771bc08 ("mm/khugepaged: > retract_page_tables() without mmap or vma lock") allowed concurrent > retraction, and commit cf4a65539c13 ("memcg-v1: no need for memcg locking > for MGLRU") dropped the walker's outer RCU protection. > > The fix is simple, so just fix the original commit so we don't have to > speculate. To fix it, pass the actual PMD/PUD pointers. This restores the > RCU-protected lookup and validation against the live PMD. Note that the PUD > handling is required as well to handle folded page tables correctly in all > cases. > > Fix generated by an LLM and sent by Josef Bacik in private. > > Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") > Cc: stable@vger.kernel.org > Signed-off-by: Josef Bacik > [ david: handle walk_pud_range() as well, clarify+simplify description, > adjust Fixes: ] > Signed-off-by: David Hildenbrand (Arm) > --- > mm/vmscan.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) Reviewed-by: Qi Zheng Thanks, Qi