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=1793439630; b=Ix6UMk1R9LBl+7vXS1McPJMhMULZbcO0MBtXp3PVGmExmms0eb1YOMDmDuNmkHKjeyg0 kkC/SaxqZww4DjyXmDpTdOqHJQzi6Z07vTl4oiOfBv1M6t0gJVaqf9lBGfq9Psn/VA3Fn EfDSLo0dlLpe/tzs+U28cowMSpHvQxbgebZYs68PN/PDfql2HTwEIGao/puov+t5C60zR Q5j5cs5vRYGuQn/2aIkx2/OlFyORnYt53meApmdJ81dUzSTwBCHftWur6wdaER7fbghHK O5waIcAbDE9TsYdbz8/8mTDcaj67AmEJuXUlchXXmFxyYVO07DCyCiYHCFsvAIKDfLg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793439630; 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=vhzYAmOdAkqyGhBWNfdsKGQhygIIdv6/ZXuoCf/3yVw=; b=BAa4l+bfjmvHtG5nNz/FfxK+kA3WizeE6Iypq98rQ052TQ6tHqyj4LA8DyviwTFnuoWL ZqJmOv1wVSwWjlR29Tx4zZzTyvqRroFKpbo8MGQT/ULjB3x0qy6B/+uChVafVSec4KLe9 OS26hBqnYft1KhqTWFdLjIAt9LRI4x1hR6rxrYpkzgqgZrM9zTIwDXUHo/hRnSK7LD9x7 0DfvgymSEXHUL1uSAf5jLwiAn9cBidiFUZ2eGXZVRYct3BGZvOj7xwB+vLT0SE9j5EmEd 6Vxolq2ohIskYyrjBok+rHtxYffmfMhd6E+ZwXtb+iDX0qUmfpK3SEuOcLrN6fhtk0w== 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=iLdA01ou; 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 BEB12606A325; Sat, 31 Oct 2026 09:40:29 +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=iLdA01ou Received: by smtp.kernel.org (Postfix) with ESMTPSA id ADE891F00919; Sat, 31 Oct 2026 09:40:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793439629; bh=vhzYAmOdAkqyGhBWNfdsKGQhygIIdv6/ZXuoCf/3yVw=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=iLdA01oulWOO6dYvCP+CtRKKHWVIi81CZdc7tIY0Dv0DRrOCh+iPbwNtueXAYD92X Qcgd0tHi3SkRiMvKjvpNjilGV1OUQyFkVExiWCHoRLnRNf3Pg5Quf82DyuCipFvJ5E eveba1t1+pQ0Frfq4xnnrxG3rjX3rvSC7U+WnP1cDs35mX/LmePYgMcd5i0fRatOpU K0EhSHEBTWngDz/8AHMg9CqlauhF73UCYeWW+kZQVnCJZdA6x8MxrgdzmYs95gNe+f Trzk2SBQLZAoy7Sv9Nr/OlxoHxjH0BXgihgLnMIG+CuFpzv14vabuGlY9p6/yQUdK9 rtmHADN+zq7bg== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:30 +0100 Subject: [PATCH v3 01/47] 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: <20261031-fixes_core-v3-1-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@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, Muhammad Usama Anjum , SJ Park , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2804; i=david@kernel.org; h=from:subject:message-id; bh=zbtgr6vf31Mknvg8yOsqXmy9ZbpWPb8teGHpWqYOrTA=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebk99XM03S8lEQljolPcxvX3C3cw/nzuZuYUnfdt6y 0Fde9XrjlIWBjEOBlkxRZag4PsGL1+uq61242OGmcPKBDKEgYtTACbirs3I8FmT9YONSo2yefGp zZ6B64/OyORR9zl9mSHu1nPmfYwLTBgZfm6qjWJeGrhwzfpj/wy9HNQMl3z9rPpC+33etU8qqzy s+AA= 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. [ 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(-) 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