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=1793306025; b=LeP87kisgwnMADIBr9tMVgQK7VJRYuUYN1ILfrqXG5lNMrFEnBGWxAeR4SxOlnPl72Xg G65qDibyVuiE3xoIe2iqafMi+C9K778PvHvXmcXyWKH6Gzn8qWbU1JS4fDQvDnL1QFSai o6dDV7GN/SyMOChKn8HMgVSb9PxFj+BNetCcHQIol1qFpAXpp669uiq+F/d1k3a/UkI5o J2yes1z+FwFtn+MeozbclOY1XXCC7EcfgXSIqH/rw6y5W2i5NCJgZxA/1g1VoshL4ULap LeHle55+Kf1OvXkrWx8zDAko/hEF7qTZMaREEZ9ijHkk7S+R5OMoyFuWroh0JZIk7cw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793306025; 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=Hl8Hja7261+PqX6A1yngTbcTCPox77BGspRqPrmbmIw=; b=LPBn4KWDn+E3jPrv0b1EgRkW36mmOqY42Kzpr37SuRSb1vMvzMoqY82UOXEyvVYElg/8 /bDAXwh4i1mKZbxUbqC17tmnPYNFgraFXjrQBZKfdRGtCPlWybohjXAG2/7mZA1Zfud/J fizrjk3MSKUixGlTFqoRQ3V0ItLjDnlekGs0ApLCMv7wFJs9k71mdVcZLb+LSjiQb+Raw C+tW8BO9AX2Gi8WSRyw98kRNZat1zlzpWxp9N3U+0KpeaJ3PMVImXQIMxvKP2QT81RIZs 6Ubh4YEak8b8F/BBYr64+KHww1rsbhv2TYO+gXhuZbTIw69D2VnY6darqfG8J972E/g== 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=BtblEQni; 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 15907606A31C; Thu, 29 Oct 2026 20:33:44 +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=BtblEQni Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6E1B1F031E2; Thu, 29 Oct 2026 20:33:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306024; bh=Hl8Hja7261+PqX6A1yngTbcTCPox77BGspRqPrmbmIw=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=BtblEQni/tV7KmG4ZsM9UPfe8T47hGMbbRdFSbdDMyagtA6eYkZbhluhI9z5BurdL 1e78U6Dqg2OUvWYcFR0R5N87ly5LSuFRTWMfolODfDF1YuUhHuMAr0b1iHsc7D3Zok WWXgLFaB/7lS8DNFBPkUEV5jhF93hksYscJQ72sXQp+mQe59teJ8lUli9p5tFfB4A9 Wz6e9K2qIY/jLVAnShYPw0I9kE8fFZ2d73v1Bo2z6zzKA/PIuyGuoriHgYP9CxUnrd fa/lB7eBUKMmE00K0RofgBKFQ5hGuNr17dEBDn3gMz8NHlng/llC5yjiUWyFxZr+iQ 1NGfRY7z8HfBQ== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:32:56 +0100 Subject: [PATCH v2 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: <20261029-fixes_core-v2-1-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@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 , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2764; i=david@kernel.org; h=from:subject:message-id; bh=kEXlYNiQWeqMYPtO5Vb4nXU0nymzCVHXtW6ux1YnkxM=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer2256v+r64KNwb7oXRXbchL8DsTsVdVJFHuRImHuO 1Xm9q1ZHaUsDGIcDLJiiixBwfcNXr5cV1vtxscMM4eVCWQIAxenAEzESYvhD9/mT2dFj7Wqffct nXRd8fk7gdkPyxdo7bD4kys6+eDSXysZ/lc7b9U16thV9e2thKX+9d0xK38eTp3Zs4hT2P0qxyT NN9wA 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) 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 9959ca158ce8..6a1af9b92349 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