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 E728D606A31C for ; Sat, 31 Oct 2026 09:44:27 +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=jvLl8q9F; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=n7/dh5mI 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=v1+ekpwjupL9b9pcbG8pHLIAFF7Z8BWbgINSpSywcxE=; b=jvLl8q9F3oHrBf rpi5KYGCKyZrz3CTaB9FDO9lKRZqCm8522/OGVW4hWYi5A/vegKglqucZalR/XxaG5uhy1Xj8PCmC YeMao/j/wgcOD8OlYaoSkEADEkSnkA/6AoYGHCr8JL8jG63RlRTrVu7fh1ecCY55K/aYJe8XmnsMu v1kYFg7xTlUG7fA+K9Y/eJ24fdr8RWkhVhzDt+/m/gxMiYifvNDc8+FdehGyzLR0bPDjNg6G9g0lB HCiue1wNntEJXtsfHdUJZMH4Hf84xClQkIXCOMKR17kza2XUHuKxANVeDFG7FKh8u9+buY62/opsp GhbAs4nDuC4rlIucxWxw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xN5dT-0000000D9tM-2kz7; Sat, 31 Oct 2026 09:44:27 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xN5dR-0000000D9t1-26m7 for kexec@lists.infradead.org; Sat, 31 Oct 2026 09:44:25 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id E864C600D4; Sat, 31 Oct 2026 09:44:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE60E1F000C1; Sat, 31 Oct 2026 09:44:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793439864; bh=v1+ekpwjupL9b9pcbG8pHLIAFF7Z8BWbgINSpSywcxE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=n7/dh5mINMOMUKO95+gONTx2Ve6Y6XcCPT+ZM+iwTwMTHVAeaRgrXb5ptLGRbx6IX HzK5Jp3M/dpYJrf4RMfNYcWQgTq4WJkZ7HXkJS42/48ivty7LdE+IOxpHHeTr0z1i4 zWePStQ24ycM28VhK6H9XTW9nXaf6Lpb7uPvj5uNMIEsTMlzWR0sC5wgghJ4aOMSi8 Kna460upm7RSYrBeisDazpPPtMuYKG2Nf7FkLefEcjo/GjwUiOdmNwc66mNiD22Sfb qFDkujgq7nV/wInZQwbFn6JzF+aKGFfRrTHfoOsRIxGN2kVPc/nK4gg/uujXWCSmEz aLn6q3dxzkAhg== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:45 +0100 Subject: [PATCH v3 16/47] mm/khugepaged: fix PMD table lock leak in try_collapse_pte_mapped_thp() X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261031-fixes_core-v3-16-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 , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2443; i=david@kernel.org; h=from:subject:message-id; bh=zTm3MuB5zSsRWepSA3fPzqAd3nAG68NQj/5HuMoa9lA=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebk/fbs00i68oY9Iep743yuyx9rcWbHl6/l2C6Hfj2 sv/HrJadZSyMIhxMMiKKbIEBd83ePlyXW21Gx8zzBxWJpAhDFycAjCRZEmG/6XFYhPUGzgPZi+s 62xe6Zsbd2BN9O57u295RvibSO1TPcLwV2DOwbcpy//vEVKP3pJ28u+ybzLuB7gsfe+ySn/tXB8 0mRUA 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=-18.9 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,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 For a private mapping with userfaultfd, try_collapse_pte_mapped_thp() takes the PMD table lock before it maps the page table for the second time. If that (pte_offset_map_rw_nolock) fails, because the page table vanished in the meantime due to concurrent page table reclaim, it leaves through the abort label, where the PMD table lock is unlocked if it differs from PTE table lock. In case the PMD table lock and the PTE table lock match, which is the case without CONFIG_SPLIT_PTE_PTLOCKS after pte_offset_map_rw_nolock() failed, we miss to unlock the PMD table. To fix it, forget the PTE table lock when we unmap+unlock the PTE table. Fix generated by an LLM and sent by Josef Bacik in private. Fixes: 6375e95f381e ("mm: pgtable: reclaim empty PTE page in madvise(MADV_DONTNEED)") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik [ david: move the ptl = NULL handling; rewrite description, drop wrong comments ] Reviewed-by: Gregory Price (Meta) Tested-by: Gregory Price (Meta) Tested-by: Muhammad Usama Anjum Signed-off-by: David Hildenbrand (Arm) --- mm/khugepaged.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 81496887d827e..34ebb37c862c0 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1904,7 +1904,7 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign result = SCAN_FAIL; start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl); - if (!start_pte) /* mmap_lock + page lock should prevent this */ + if (!start_pte) goto drop_folio; /* step 1: check all mapped PTEs are to the right huge page */ @@ -1935,6 +1935,7 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign } pte_unmap_unlock(start_pte, ptl); + ptl = NULL; mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, haddr, haddr + HPAGE_PMD_SIZE); mmu_notifier_invalidate_range_start(&range); @@ -1952,7 +1953,7 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign pml = pmd_lock(mm, pmd); start_pte = pte_offset_map_rw_nolock(mm, pmd, haddr, &pgt_pmd, &ptl); - if (!start_pte) /* mmap_lock + page lock should prevent this */ + if (!start_pte) goto abort; if (!pml) spin_lock(ptl); -- 2.43.0