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 AC727606A324 for ; Wed, 28 Oct 2026 08:20:35 +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=SNqNQyvg Received: by kanga.kvack.org (Postfix) id A2F776B05B4; Wed, 28 Oct 2026 04:20:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9DF416B05B5; Wed, 28 Oct 2026 04:20:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 87FC96B05B6; Wed, 28 Oct 2026 04:20:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 404846B05B4 for ; Wed, 28 Oct 2026 04:20:34 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id B3236C0BE1 for ; Wed, 28 Oct 2026 08:20:33 +0000 (UTC) X-FDA: 85371338346.10.C86B857 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf06.hostedemail.com (Postfix) with ESMTP id EAF3B180005 for ; Wed, 28 Oct 2026 08:20:31 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=SNqNQyvg; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793175632; 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=FU6Km7ChT8wB3iaSth+F3/69ecBIaf5N/Fzbc/bbo+s=; b=Wkj24gX419h2RsD/E0gbxJeECJ80mEoFlbMWTZYfzZC1f9dA494okjwHfJyOg7s2WV0SPH cOxjHV1y5FpL+zF7mh+Vskrq0qwo2t3upm6sD8QJSlm2sLFc9H+PdObUjeZzQk64FZxn3e 3ZOPippOtMhgJWT3XvwXHm9NeIreIgw= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=SNqNQyvg; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793175632; b=uenfLAPjltQn0TYhxw/XVLjzzSiBi+Vcg7YeO28aMUl1+zpJuriy0KXWc64cRUQl2s5STe EPZcoN9XgbuOaipyXif4qmQL2qGbDrzs8P2sc7aduyTMOwrOg+q2afGvpLkI/VUL8sBTNh WTETJsgkp8BR5UxmMF5F7skYrwWHRx8= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 1F2D341790; Wed, 28 Oct 2026 08:20:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 646B11F01825; Wed, 28 Oct 2026 08:20:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793175631; bh=FU6Km7ChT8wB3iaSth+F3/69ecBIaf5N/Fzbc/bbo+s=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=SNqNQyvgTJLYYki1VSd8Hcl0rY46o6Ox7LSXYq2rHJNhZE9s/g3SgZzKk9TbyXUej QsuLPUFbAhBZHeHF9UWjLtam007zqSERpnh+0tGF74wfWrl+sLxVERrxh0sBw/OOlK peUvcnC/7tdlAtykO+TZoTPoFFw+PB3f3piMINdC5IaYi/RN6nqY0rSmn8TNYUXbmN gR3tsZvNx9LO6bnBOLFwK5LVL9+iXZdynSfHTGPwCtgL75QSBCLou55YFOuqsxmPFR f88pw2cwS9M9t1RMNZr3D4E94Ab0LPajqMQgHoQgM1wtehcupx1k15Uja9JjYn2IIV l8lmiV4u8XSkQ== Message-ID: <6633e2c9-d4c1-49f0-a4a9-433fcd8b3337@kernel.org> Date: Wed, 28 Oct 2026 09:20:12 +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: Barry Song Cc: Pedro Falcato , Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui 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> <22b819a2-631d-468e-b724-770caf9f94e4@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: EAF3B180005 X-Stat-Signature: d5ef1u4bt59wo9967n1hd6xb6bbhq54c X-Spam-Status: No, score=-12.3 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-Rspam-User: X-HE-Tag: 1793175631-200232 X-HE-Meta: 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 JcwlN3fv NfPS1s0sIQiebj19HEZ1VEnXAGSJjEZtMbmkPaBVht3erxI7YTyfG7kI6yAeDNbr/sIniHm4Y5A2m58Mvflaun7FQ3CPQJogyQorvqKR+ZziHQSIOegXhHokb08+O2KkmKUMUN8ipMoSruteJbf+oeS9H44J/q4UKbl2NFxC7xsdVQ6A3fx2HqvG29mgCIPwSGpv5hbs4Udy/xdEACeDeVek/NbgWcPc5GeuwJTiaidCtefsmvTkCWuEajgbjrzzmsYLPaLhhJWXMw8+EN+0dnSY/hj8qou2yQPw+wYaDHjd/aK95Ku8fBL3bekUZsXviB1UBDuB28NNyjr8u7OJSqUdPA9FJNODFVti6fZCo8UhIVPHHQ25y5vvEZz/DOYAaEwaDyODA+Prnq0J/iyAuHAv2wdY80++abQfmxFFr07/G0IwOGUMvpLLtTBPtrg4WVW6PxrZxCEPr4tQ= 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 20:48, Barry Song wrote: > On Wed, Oct 28, 2026 at 3:07 AM David Hildenbrand (Arm) > wrote: >> >> On 10/27/26 11:38, Pedro Falcato wrote: >>> >>> 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 ... :) > > Regarding the race with memcpy(mm, oldmm, sizeof(*mm)), we > still have one [1] even after this patch. > > That is, copying mm_struct can happen concurrently with > lru_gen_del_mm(). However, this race doesn't seem harmful. > I might be missing something here though. Do you have time to look into the issue, to see if it's actually still reproducible afterwards? Likely we want a separate fix for that on top. (or mark access as valid racy) -- Cheers, David