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 81FEC606A32E for ; Mon, 26 Oct 2026 23:18:16 +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=DN6Kvemy; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=N0Io6SX8 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:Cc:To:In-Reply-To:References :Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=NUBP2xRnXTWkvkzljjau88QTTUDveY6Hz9RAZJBGdTA=; b=DN6Kvemy7vS9CM DIh0/eSS0qC1i1YXt/E+xrsikWTMhaCL5K3HYlcNAHc73V/VE+OHFWPfqm5PkSVmRMXcv/EnHFbR3 OMUEHwJ898ZGBydejbzlxB6DUV+zI8wgkhoc4XlZrRXuXIB2awrFvkxT8vnGdU0Xd5Fsn5q0M+AQS N2u3DUl4vaFXEatUvaluRNlhfo74NoHgTJYAEFXFmlA3c+n3/h0iFysEndKJGJy5+Id5jnS6lcLTf jKJQFXVHTBLGDtOx2EXWsVKJuyqvr2PLKARUhgvxfb3mHONMHEbCanYnKArvThT8qzL6TRhVThtfS gw/bdl/qtOguCqBtULfQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLTxI-00000003OyZ-0wi5; Mon, 26 Oct 2026 23:18:16 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLTxH-00000003OyD-0P96 for kexec@lists.infradead.org; Mon, 26 Oct 2026 23:18:15 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 7390C4095A; Mon, 26 Oct 2026 23:18:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4034A1F01828; Mon, 26 Oct 2026 23:18:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793056694; bh=NUBP2xRnXTWkvkzljjau88QTTUDveY6Hz9RAZJBGdTA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=N0Io6SX8cBzzTDOb7cpNCY6FTZU/h+KZanqCjpiuERrlKcwqPUmds2XacPzDJEdk4 PYZRLj+AoUQoLE6z+36JUW94y4Bp88f3cJod9gQlvbGbNdqQlAhw18OBaLdHFRSS/q AmNfMdre4JdR5YYAE/k4Rm8QdRbDk1YvBQqj3ljM08SjJ/W5VLEH6Of+WTIkuE7YcM aAnkYNndmFBxnm4FtuLiESvFhlCip+lgP5vzefuhDl3xbxXkMESzxxRjpavTYuronn umBEwX+v+06COBgPtWP50OU+jEh3Dd9mcFm9RqijNKNh6N3UEEBuJYsTMOvJ5UqGVT OMLDSeCDpWsOA== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:21 +0100 Subject: [PATCH 01/46] mm/mglru: don't use stack pointers when walking PUD and PMD tables X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261027-fixes_core-v1-1-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> In-Reply-To: <20261027-fixes_core-v1-0-6f74bec9a5bb@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, Josef Bacik , stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2223; i=david@kernel.org; h=from:subject:message-id; bh=35PvaXKWWy0wg30tuDie4oWbed0+71n+0SGauq9bLs4=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu35+kxCFy6tE/r17VSuMD+w0ueUdwpk73e7hsKZNdZ IP9v4zojlIWBjEOBlkxRZag4PsGL1+uq61242OGmcPKBDKEgYtTACZyJ5nhD5c65/fu+Q1lbuVX lQuzF8Wx5tbVeTgvc1zKKt+8aWesCiPDfdkuFpbL603lW0oeZNmsVj9stXrGL6G3u6s954V9rgn hAwA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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=-19.2 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,USER_AGENT_GIT autolearn=ham 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 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(-) 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