From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793056695; b=GO33VFZrWjrb0SRVlRgjzBX7Pc+fp2Lh4AZkDeX7oAvlDBIm7d43I1ZIiUaP+YKzvIZt 7M8odBJvFL6dvLQaJDzc6+q2QEINk9HS0f4Ho/Nm5AfalFEeH386lgUED09qUEpHNPExq v2v0BMid7kwTImw/Vo0PzhR6bFe/5XugpYy/wii93r88vHCsNdtukMZOYj2kM3B627EDG bEuq/H3woNajloJj/Z6RqoHUUbIWujtvm3Cse7XtY5GnhLSM5wrwOhDc/M0mlqDw+JIGT 6ctBH8tWqcnrgY/XMXB+fjbHQmu4SD35ntgNbf7nvMJjvHACwOLMrw+9NtY0bkcoqHg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793056695; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=NUBP2xRnXTWkvkzljjau88QTTUDveY6Hz9RAZJBGdTA=; b=UFmn7+0ZuFAX8NCXAbFYa9t5pX/mvCXGmS2AceWq9SDovZ8rEMTnnqs4gebvgf3wYXte TQcwZTZXBu00z8VKBcsQ0PiLs+G8Q64q0pQ2YKDhlLMz3OaoJWd58r3Czr6DgSu8H2Ssf NYxxYWmOeAlxV2nOOslmWh3j7lrZjSxegKhEOGev1UKu1CjcxKYiliBkddgaS0O3AB8rh kTAJmbTIIFSgodFWJwSr1GA7V6sC5V+qU4dcgLMOF9WMV+d4iztwEvrqBRsAZqccSERM8 8VfeREYPzIs/gqMAxF079R3WAVmpKCCYI5dtRSlU2AvhRzrz7kXxiBZTCyNjVTHn6Xg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=N0Io6SX8; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B8EEF606A31A; Mon, 26 Oct 2026 23:18:14 +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=N0Io6SX8 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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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 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