From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC106C5AD49 for ; Fri, 6 Jun 2025 15:34:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2B2426B0092; Fri, 6 Jun 2025 11:34:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 290396B0093; Fri, 6 Jun 2025 11:34:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 178FC6B0095; Fri, 6 Jun 2025 11:34:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id EF1CB6B0092 for ; Fri, 6 Jun 2025 11:34:05 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 98947100BD6 for ; Fri, 6 Jun 2025 15:34:05 +0000 (UTC) X-FDA: 83525371650.28.43F6487 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) by imf25.hostedemail.com (Postfix) with ESMTP id 50B3EA0007 for ; Fri, 6 Jun 2025 15:34:03 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="BlffJf/D"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=hGHpgx7E; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="BlffJf/D"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=hGHpgx7E; dmarc=none; spf=pass (imf25.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.131 as permitted sender) smtp.mailfrom=vbabka@suse.cz ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1749224043; 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=SlwW0J0385Y0bArYP2SUZCYXr9QqXS7xayaGmcRxHrI=; b=1dwlx22LwlHc2pRgWd/XfHCgJAuggEUpJEr84JjoZxeJcSbYjzEw+xYYpS0ZiWC29+BMXh PJ41DiL6hP7F6oij5YMg1etdJ46R8SIoc5BG876E3oXFMbYfFb/KiZ3I7pT0GmruUjpqJd elAkkNAcFrjFLAzJke+F4p0FkW0yjtQ= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1749224043; a=rsa-sha256; cv=none; b=CBGICrkiTozHJkhSowCXqabQ81y9KRmCbpyjnAD5r+FPSNxbuV7WsRSReWY4LU8/7atvLP eRxK2d+ToHNUAJPO9jdVBB5OYFwrbUN2rgY8LL/VmJPP9rWEUFCu4AWPq0+asfzOmQLWGI XZSEj1h6xc0QsMuJJ4i+BaYgPaw3EDY= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="BlffJf/D"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=hGHpgx7E; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="BlffJf/D"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=hGHpgx7E; dmarc=none; spf=pass (imf25.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.131 as permitted sender) smtp.mailfrom=vbabka@suse.cz Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 30C701F7AF; Fri, 6 Jun 2025 15:34:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1749224041; h=from:from:reply-to: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:autocrypt:autocrypt; bh=SlwW0J0385Y0bArYP2SUZCYXr9QqXS7xayaGmcRxHrI=; b=BlffJf/DBrN5guDiHTn0NQPpKU7mMuHbwBoSgvGqSJD+AhxjnE85osPIFTdzS2ph5vH8ny wrILZp4VyPV0yO+osD9vJaNwOXVDnW5E+vSyuiZ9STCTuEYfrod06qX9sA3cz52fOh15tG AxaWABKIcXvwfUMPEikLBL3weUsOXZk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1749224041; h=from:from:reply-to: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:autocrypt:autocrypt; bh=SlwW0J0385Y0bArYP2SUZCYXr9QqXS7xayaGmcRxHrI=; b=hGHpgx7EGs+9pq7TLA28HHzDvffqXl+pWlyrywYRA25G2gCoCgYcAwBsyHtlrM0tYQA88w wh3wuaYX5H13mKAw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1749224041; h=from:from:reply-to: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:autocrypt:autocrypt; bh=SlwW0J0385Y0bArYP2SUZCYXr9QqXS7xayaGmcRxHrI=; b=BlffJf/DBrN5guDiHTn0NQPpKU7mMuHbwBoSgvGqSJD+AhxjnE85osPIFTdzS2ph5vH8ny wrILZp4VyPV0yO+osD9vJaNwOXVDnW5E+vSyuiZ9STCTuEYfrod06qX9sA3cz52fOh15tG AxaWABKIcXvwfUMPEikLBL3weUsOXZk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1749224041; h=from:from:reply-to: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:autocrypt:autocrypt; bh=SlwW0J0385Y0bArYP2SUZCYXr9QqXS7xayaGmcRxHrI=; b=hGHpgx7EGs+9pq7TLA28HHzDvffqXl+pWlyrywYRA25G2gCoCgYcAwBsyHtlrM0tYQA88w wh3wuaYX5H13mKAw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id F389C1336F; Fri, 6 Jun 2025 15:34:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id f5UjO2gKQ2gaLQAAD6G6ig (envelope-from ); Fri, 06 Jun 2025 15:34:00 +0000 Message-ID: <2b6cce1b-5ca4-49d2-8a33-aeae1543ddc6@suse.cz> Date: Fri, 6 Jun 2025 17:34:00 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm/memory: ensure fork child sees coherent memory snapshot Content-Language: en-US To: Jann Horn Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, Pedro Falcato , Peter Xu , linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20250603-fork-tearing-v1-0-a7f64b7cfc96@google.com> <20250603-fork-tearing-v1-1-a7f64b7cfc96@google.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 50B3EA0007 X-Stat-Signature: yswijs9qfbkupc99gpto56bw89m1k173 X-Rspam-User: X-HE-Tag: 1749224043-646286 X-HE-Meta: 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 n7NUF/zN 6Lna3aETdd3kj1F21bz/HncouEs+4Fne2T8ILULrStWPVoGBmlMb30t3qa1nG5VCeS/MbEiV2m1P236s06ESe3y0wb+BxvuwUOApd9RXKJLWgfAI2PE/MDEV9/zzvGB79wHPb4UCsPZfwywyELduiTzTqebX2ULDwnewHgnSMVsvBKwz1DiCdDELFVteK9KyBB8QHwCXiLCq4WicKPG5RiNP9VoPEqOFPZwYZyWqH1ScN0mlyRoCXKF8xrnyOBBByCAsBobDxR6qDTTutjUw48jVlBgFgpqiLO+/wk8F75rf8h87gG6ExS5OtXBlLkTp8Bek1VyIHqJ0CvBzt5+Ek14gcmCTvUZxftS4p85BY5aY+FIA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/6/25 14:55, Jann Horn wrote: > On Thu, Jun 5, 2025 at 9:33 AM Vlastimil Babka wrote: > + * - Before mmap_write_unlock(), a TLB flush ensures that parent threads can't > + * write to copy-on-write pages anymore. > + * - Before dup_mmap() copies page contents (which happens rarely), the > + * parent's PTE for the page is made read-only and a TLB flush is issued, so > + * subsequent writes are delayed until mmap_write_unlock(). > > But I guess this way makes it hard to review patch 1/2 individually. > Should I just squash the two patches together, and then write in the > commit message "see the comment blocks I'm adding for the fix That would be good unless it makes it increases the conflicts in stable backports. > approach"? Or is there value in repeating the explanation in the > commit message? Depending on the above, if the stable fix needs to stay minimal, it would be valuable to make it more self-contained by repeating that in the commit message. So that the LLM has an easier job marking it as a CVE. Vlastimil >> > Fixes: 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes") >> > Cc: stable@vger.kernel.org >> > Signed-off-by: Jann Horn >> >> Given how the fix seems to be localized to the already rare slowpath and >> doesn't require us to pessimize every trivial fork(), it seems reasonable to >> me even if don't have a concrete example of a sane code in the wild that's >> broken by the current behavior, so: >> >> Acked-by: Vlastimil Babka > > Thanks!