From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 75523606A31A for ; Tue, 27 Oct 2026 19:07:30 +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=jf1fDspo Received: by kanga.kvack.org (Postfix) id 56F7E6B05ED; Tue, 27 Oct 2026 15:07:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 549076B0761; Tue, 27 Oct 2026 15:07:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 435A56B0763; Tue, 27 Oct 2026 15:07:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 10E986B0761 for ; Tue, 27 Oct 2026 15:07:29 -0400 (EDT) Received: from smtpin07.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 881F9140AD0 for ; Tue, 27 Oct 2026 19:07:28 +0000 (UTC) X-FDA: 85369339776.07.D5F25CE Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf07.hostedemail.com (Postfix) with ESMTP id BF5554000B for ; Tue, 27 Oct 2026 19:07:26 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=jf1fDspo; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793128046; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=4JNAgIKFjPRpfv1PgOMbYf97LYfRcFa+6eIVMdPRyjw=; b=k1M2vAnv/VPw/8oJsv6rrmTw358Yi5xSzmWbz38tf9HGlbvPiUj0aRVNeexk1VEf64qIRX OnFkFi+vN1b8NMIl0+hULf5GfwjiLKNXqKWStCQ1o4Y1yRR47ThIAylhbn62y7udh4Zrxv Vq1MqZ5dCCiAYs8kixy74eED/Dvuavo= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=jf1fDspo; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793128046; b=R17tJ8f564p6uuanK6X4EAujDjY90rkiSOUclqoEpqznIzXn0QIYO6c0VahlViTcquaDZD H4CKgvG6aH2MMXfrLOJ5RrNTSh5i1AJbXOwnehICM/OgHHZKSsoFmCbjzQiZsoBvch0qpK Bm4l7PwIVTTjp/lowMTxqKdhRqoa0q0= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 5779E60136; Tue, 27 Oct 2026 19:07:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 729AC1F01825; Tue, 27 Oct 2026 19:07:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793128046; bh=4JNAgIKFjPRpfv1PgOMbYf97LYfRcFa+6eIVMdPRyjw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=jf1fDspo2NgWYuI74LdGEBcYt8altR6P9yRUKqtzDSTFSAnWIf4GPYCpU6SCH2cR4 kLKqYwz07l5Zxzm/sG06VNfh8M3YEXLg0g/xDRdxPgQdpFPjuVEjR01moMhjRlhF+T pjPpXSza1JiJ6vbP0VDvf6JnPlSg5bHKRMHCf8gjvuKNvnjEbklK28yyR7bqqPh8uC LRmuSQyxUKj9WGQhuRHWgrbDg7s+hLnc2B2yj63yqn4Wai5qpm3fBCxoqPXWBL+olg 28HWBF3L63ZWkWwiog+dmsXfZtM+0ZeN1bDPXJhSyQqkRos7H6AArQhBQMI6vYISQY 8xVSAIg2hJR+Q== Message-ID: <22b819a2-631d-468e-b724-770caf9f94e4@kernel.org> Date: Tue, 27 Oct 2026 20:07:06 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/46] fork: take mmap_lock before copying mm_struct To: Pedro Falcato Cc: 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 , 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 , 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, stable@vger.kernel.org, Josef Bacik References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-2-6f74bec9a5bb@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: BF5554000B X-Stat-Signature: eji8gx5dee7gnzcmgikfcgp5ben4k4b5 X-Rspam-User: X-Spam-Status: No, score=-12.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1793128046-863864 X-HE-Meta: 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 0itbu7gP GdvQwi4j1QfHoKc366jlVljoSyVan6XqtvZeOFPF8baLQBhI9gQk0lM2bQ+VfXfdZmunak/dOnq+QK83O+FaD411c7iUp09Wx4VmRrRhAwXV3iUFaXdn29FuN6ZStyhMgFuhc94diyHucsSzuGPZfI41IxxCed0BFEya6Ccpuv1MRri83oUDk6c8KruZv4ThJSCziHNBzwY/KSA2jgNUGjfXw4/Bhc3TkdlIy75tMgQ3Vy8Qtt2rrgAJGjg//kqWUs7Y8Apb8ec6S4myUvWiIXC6ttQWY0wfK0F0JrCgQIlyi9XKV/IB/rAXz/xcDjF8+QZl3ogE4LmGplf9wGETHRAZnXIk1Rdt9CK7BLo7PUyFFAZA4UP8jobxEgN2yjkcDlaGCTiNg0mcB5O2JZTIWOLrdYd0qNAUkv/qbAObXBbhg3rNwrLvfu6lysf2fng/zPswJ1p1J3vH5hdPYGVwipFU1sQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/27/26 11:38, Pedro Falcato wrote: > On Tue, Oct 27, 2026 at 12:17:22AM +0100, David Hildenbrand (Arm) wrote: >> dup_mm() copies the parent's mm_struct before dup_mmap() takes the >> mmap_lock. A concurrent brk() can leave the child with a stale mm->brk >> and newer heap mappings, causing later brk() requests to fail. >> >> Other operations (e.g., PR_SET_MM) on the parent's mm_struct can similarly >> cause inconsistencies. >> >> As a simple and robust fix, grab the parent's mmap_lock earlier. This >> way we don't need to update individual mm fields in dup_mmap() and >> keep missing ones. Stop updating the 4 existing members (total_vm, data_vm, >> exec_vm, stack_vm), as that is now no longer required. >> >> Keep releasing the parent's mmap_lock in dup_mmap(), before >> userfaultfd completion, to avoid moving the userfaultfd handling into the >> caller. This should get cleaned up later. >> >> Move uprobe_start_dup_mmap() to preserve the lock ordering. >> >> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") >> Cc: stable@vger.kernel.org >> Reported-by: Josef Bacik >> Reviewed-by: Lorenzo Stoakes (ARM) >> Signed-off-by: David Hildenbrand (Arm) > > Reviewed-by: Pedro Falcato > > FWIW, strictly speaking malloc() isn't usable in a forked > (multi-threaded) child, but glibc/musl provide this in a best-effort way. Yeah, I'm more concerned about other things that can race ... :) -- Cheers, David