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 7B3E6606A32D for ; Sun, 1 Nov 2026 03:18:03 +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=p/Q4ETTt Received: by kanga.kvack.org (Postfix) id 855B56B05B2; Sat, 31 Oct 2026 23:18:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 806716B05B3; Sat, 31 Oct 2026 23:18:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F5AD6B05B4; Sat, 31 Oct 2026 23:18:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 455476B05B2 for ; Sat, 31 Oct 2026 23:18:02 -0400 (EDT) Received: from smtpin26.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 891D11A0778 for ; Sun, 1 Nov 2026 03:18:01 +0000 (UTC) X-FDA: 85385091162.26.8B76AF9 Received: from mta1.migadu.com (out-139.mta1.migadu.com [95.215.58.139]) by imf15.hostedemail.com (Postfix) with ESMTP id 72B7DA0002 for ; Sun, 1 Nov 2026 03:17:59 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="p/Q4ETTt"; spf=pass (imf15.hostedemail.com: domain of baoquan.he@linux.dev designates 95.215.58.139 as permitted sender) smtp.mailfrom=baoquan.he@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=1793503079; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Z6x5MIctxHa9/j/zlx7zweNCYHHtp8racH88QViVO7E=; b=FausC22Zk+NnEZTOczIOPo/mSacAObxZZ5PRz3Js20/bjEWocEBbNE0t+GBrCoXsQIV2qI 1h/7SuNEtIIF+93CmntqIfRWEapoJzeIS3o+hIOzyr8gPeuCNxPmgfFtA3ZginPg4syYq5 RK+ia1hStIa3ra/P1TR36waKbXt0YYA= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793503079; b=MpZ81QMZOZVRNyFRskQa6AxQLJNR0fNGFETA3Lx46ZoQI3TBCCM0mnhtC32eMeS5sXI090 n9p8g++kT2S1eZogRdfkR3UCQWNlkElIiQfY/NYhu2r4+/tTEUJ7RY8QM9spnXhwm1wj5B BF+Hy67Nf65d2rebGb6RHiuWuwA2ZlM= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="p/Q4ETTt"; spf=pass (imf15.hostedemail.com: domain of baoquan.he@linux.dev designates 95.215.58.139 as permitted sender) smtp.mailfrom=baoquan.he@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Envelope-To: linux-mm@kvack.org DKIM-Signature: a=rsa-sha256; bh=VqvV8qpM4mS5SY0ZFKzHPcZcEDmnWQFJ4Ho78vSEfFk=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793503078; v=1; x=1794107878; b=p/Q4ETTtIC16vjBAdv8+ISuTf0FXF9cgntxqj25Zl5aIfG1jL2F0WbNloasy9A7EoIVpIFOr OxNrtrDS+/8yGvz1wt4ceJoaCmPzh5TpOQQ1e5tJ/a9TBWUPDyrRr4BKmkx4z9zaG7vrKKwqfCV BxONu9cspI2Vmlgf0XZ8Mkzo= X-Envelope-To: linux-mm@kvack.org Received: by mta10.migadu.com with ESMTPS id 83615b79e9b3fb35; Sun, 01 Nov 2026 03:17:57 +0000 X-Mizu-Trace-ID: 83615b79e9b3fb35 X-Migadu-Flow: FLOW_OUT Date: Sun, 1 Nov 2026 11:17:50 +0800 From: Baoquan He To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , 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 , 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, Muhammad Usama Anjum , SJ Park Subject: Re: [PATCH v3 01/47] mm/mglru: don't use stack pointers when walking PUD and PMD tables Message-ID: References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> <20261031-fixes_core-v3-1-d6437171ecc3@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261031-fixes_core-v3-1-d6437171ecc3@kernel.org> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 72B7DA0002 X-Stat-Signature: 38j1cmfg9pqu54rf6jfwcue59rg9qwzo X-Rspam-User: X-Spam-Status: No, score=-15.8 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 autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793503079-67025 X-HE-Meta: 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 yz1Fyw2M 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 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 10/31/26 at 10:39am, 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. > > [ david: handle walk_pud_range() as well, clarify+simplify description, > adjust Fixes: ] > > Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") > Cc: stable@vger.kernel.org > Signed-off-by: Josef Bacik > Reviewed-by: Rik van Riel > Reviewed-by: Qi Zheng > Reviewed-by: Dev Jain > Reviewed-by: Lorenzo Stoakes (ARM) > Reviewed-by: Kairui Song > Tested-by: Muhammad Usama Anjum > Reviewed-by: Harry Yoo (Meta) > Reviewed-by: Barry Song > Reviewed-by: Baolin Wang > Reviewed-by: Pedro Falcato > Reviewed-by: Kiryl Shutsemau (Meta) > Reviewed-by: SJ Park > Signed-off-by: David Hildenbrand (Arm) > --- > mm/vmscan.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) LGTM, Reviewed-by: Baoquan He > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 9959ca158ce83..6a1af9b92349f 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3911,7 +3911,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, > > walk->mm_stats[MM_NONLEAF_FOUND]++; > > - if (!walk_pte_range(&val, addr, next, args)) > + if (!walk_pte_range(pmd + i, addr, next, args)) > continue; > > walk->mm_stats[MM_NONLEAF_ADDED]++; > @@ -3947,7 +3947,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end, > if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val))) > continue; > > - walk_pmd_range(&val, addr, next, args); > + walk_pmd_range(pud + i, addr, next, args); > > if (need_resched() || walk->batched >= MAX_LRU_BATCH) { > end = (addr | ~PUD_MASK) + 1; > > -- > 2.43.0 >