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 D5C8A606A324 for ; Sun, 1 Nov 2026 03:18:47 +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=L9a9B1FD; 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 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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Unsubscribe-Post:List-Owner; bh=Z6x5MIctxHa9/j/zlx7zweNCYHHtp8racH88QViVO7E=; b=L9a9B1FDVc8dxk6ZOz+wLCAs+G fc1BDvGtQH52ovol/XMW3PwzzPycn7VzY9Pq++KfPidYW+4glwXhJkap7icnr6ov24L7PHz+tRnFq eghZWmCIgtyXXcqtLPR6QB6no04KIk9cw534rHNcVLjIQUERgBBrSwlIvfcnGeiioSTwtkeRnizPj h52hw0OsUIe7Aav3AR/KA5/SM/TgWHY3GvV4DJJYyvMUqqvKPghQgS8PGHkmk0tr7Fz1SyLtedqIb nvs29NFxWrlayEUdLXL0VK/0pooVOb4yTiM6qXsINe1Wb86oONASQCY9w0dILwQhfF+8ooJuxRjnU l0nOPb8w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xNM5l-0000000Dpqw-14VS; Sun, 01 Nov 2026 03:18:45 +0000 Received: from out-111.mta0.migadu.com ([91.218.175.111] helo=mta0.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xNM5f-0000000DpqO-2i4B for kexec@lists.infradead.org; Sun, 01 Nov 2026 03:18:44 +0000 X-Envelope-To: kexec@lists.infradead.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: kexec@lists.infradead.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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261031_201839_915679_E3339495 X-CRM114-Status: GOOD ( 20.89 ) X-Spam-Score: -2.8 (--) 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=-15.9 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 autolearn=unavailable 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 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 >