Received: by 2002:ab2:1689:0:b0:1f7:5705:b850 with SMTP id d9csp1604698lqa; Mon, 29 Apr 2024 13:23:03 -0700 (PDT) X-Forwarded-Encrypted: i=3; AJvYcCU8EZgTwedJ2v4gu7pqLR+gd7ImRzJtoPwYxLvbj0oazj4jXyOVAfxkeSWZaoWbSvkW7Qqbs36elR48VyZbyvLKDhappPen3oGzRABc1w== X-Google-Smtp-Source: AGHT+IGdtMh6cWKnHUbQAP1ZJ/N8OfbVMcdtOcsM6u+eoYeQFiFnM0rN+xwEjsoLZ8FYjfPII4s1 X-Received: by 2002:a05:6870:2052:b0:221:8228:ae32 with SMTP id l18-20020a056870205200b002218228ae32mr10094401oad.28.1714422182497; Mon, 29 Apr 2024 13:23:02 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1714422182; cv=pass; d=google.com; s=arc-20160816; b=Wwqvb3lAFqANJgb5Yf26c7lg7NIUQsC4O7NkRBGL5eigmZ+RKb8L74+2UHJyyZCMe9 3IZ3TVIcuQla/QZM96Sku/TVwWritpTRaArgdd80qR36ddISkLxgNm8xl/7N2p5552Gr VLaqFnYu3JbD5VPAnzm04pYf9FyFxZRN1J+nFNTIBUs9Uj0wtlFlRiMni1WQJHcenZlB pXT/RbhzS9BXbyl17ZcifA2XlS4BUgZTagbeQq7L9xwTB5wbP33rnPOOJ29Mub56yl4i lQJd45Fsz839unxub8LzzP4nMqvhCP83tbSlk2ZYAR1sBxwi9lzfyjmGfllADQJTSeUz 6Gpg== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:in-reply-to:autocrypt:from:references:cc :to:content-language:subject:user-agent:mime-version :list-unsubscribe:list-subscribe:list-id:precedence:date:message-id :dkim-signature:dkim-signature:dkim-signature:dkim-signature; bh=wbbou26awthy0OaHOCg1E2oWXEWL2HTH0voxKWq9DDA=; fh=gFOhxZbuA9MruqGtXBFYfpv+s7WkSW2VWztejIlAauo=; b=rUifof4fknWRsIQbaJWcqH9AWBV5dIgDgCWZs1h0N7Bue9rycSW66X8g64u1V+3r1R Lc8cF01v/ZgBkCDncSRk28UYPrHYSto9OpFMjVAzXXyiy8MS8fs+GaaQxwv2x7le+AYp niKk1rh9S6HrnkknXCNpOluT50EF9R9HSB8NJsWjNymsFu1zU/qtcHXr7aIIetBRavMO /jMt7fi7wL12b/eFiesun7korCSINfLGhvDAb9qA2arp/sF5sCVxkJsimp+Y6nDc88Ts LW4RLkmr+dN2IGDr6dPk6IhQtgZbRa/z4KupbHe3Sgx+ep3SqHOuXT6SpSVIukqncdP+ LfBQ==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@suse.cz header.s=susede2_rsa header.b=XUqsYLc5; dkim=neutral (no key) header.i=@suse.cz header.s=susede2_ed25519; dkim=pass header.i=@suse.cz header.s=susede2_rsa header.b=XUqsYLc5; dkim=neutral (no key) header.i=@suse.cz header.s=susede2_ed25519; arc=pass (i=1 spf=pass spfdomain=suse.cz dkim=pass dkdomain=suse.cz dkim=pass dkdomain=suse.cz); spf=pass (google.com: domain of linux-kernel+bounces-163012-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-163012-linux.lists.archive=gmail.com@vger.kernel.org" Return-Path: Received: from ny.mirrors.kernel.org (ny.mirrors.kernel.org. [2604:1380:45d1:ec00::1]) by mx.google.com with ESMTPS id vq9-20020a05620a558900b0078d4b620c82si26855007qkn.609.2024.04.29.13.23.02 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Apr 2024 13:23:02 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel+bounces-163012-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@suse.cz header.s=susede2_rsa header.b=XUqsYLc5; dkim=neutral (no key) header.i=@suse.cz header.s=susede2_ed25519; dkim=pass header.i=@suse.cz header.s=susede2_rsa header.b=XUqsYLc5; dkim=neutral (no key) header.i=@suse.cz header.s=susede2_ed25519; arc=pass (i=1 spf=pass spfdomain=suse.cz dkim=pass dkdomain=suse.cz dkim=pass dkdomain=suse.cz); spf=pass (google.com: domain of linux-kernel+bounces-163012-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-163012-linux.lists.archive=gmail.com@vger.kernel.org" Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id 2B22C1C21DB8 for ; Mon, 29 Apr 2024 20:23:02 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6CBDC1419B4; Mon, 29 Apr 2024 20:22:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="XUqsYLc5"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="CPyUBR9r"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="XUqsYLc5"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="CPyUBR9r" Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 424AA12B14F for ; Mon, 29 Apr 2024 20:22:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714422177; cv=none; b=lqeWQGTJeifVDPo+i0slKfB22nPasDvfvlXBzwZfYSnh9Wlcj2OJINgBl508qQ5nm5MzyFHFtTCBZ9uxag4UCmxf/0kzHaxEi7RboO6nOGP6x4HL5DHKai5BreagOsrzzQ3GlYDB6XL/2/ZOgmlo+DyIFARVv73t28jDS58Mih4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714422177; c=relaxed/simple; bh=TVcBTI0zuiXuSOE4Jt9svSMfs/4dmk6pHHcYqL/PMNo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ldRQiH72kRyCv2aVcBxMGK0qKPSKnR99XQTBKTJIWip/eRdEWcgDxInaGdmtDV4rlb3o99vJeN2kR4+8tTNrzzD04oKdKkLIZmCll8DOIclphRji7qEzED62uQIQDkFb2ky+Rd1/L3nx5tsL7WlsT3YgvW/B7wB31+tiA7ZNq00= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz; spf=pass smtp.mailfrom=suse.cz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=XUqsYLc5; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=CPyUBR9r; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=XUqsYLc5; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=CPyUBR9r; arc=none smtp.client-ip=195.135.223.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.cz Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (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 12B151F395; Mon, 29 Apr 2024 20:22:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1714422173; 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=wbbou26awthy0OaHOCg1E2oWXEWL2HTH0voxKWq9DDA=; b=XUqsYLc5gfh0LAKx12R6+M+W4IJZPigGJ/3s6aDE1q7G/hANgybUZ79zcRC8Hz5JOIk0nS D8hdut82Fezbia7vt9WgoI4pnveWsk/WzqpFoCfeFEi5RHp6zXicDUrn4IyDDEPMkA/5FZ 0rmVl2aVUNQdOsrCVsu0lCfijoETxSo= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1714422173; 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=wbbou26awthy0OaHOCg1E2oWXEWL2HTH0voxKWq9DDA=; b=CPyUBR9rDR48D+9U35W2mWlSuIsVW++99Mmknu1ZGKRXGQHZVZAuNFekhbtY2gNDt3Y3FP Ye8CzcQ9vNSO4XAA== Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=XUqsYLc5; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=CPyUBR9r DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1714422173; 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=wbbou26awthy0OaHOCg1E2oWXEWL2HTH0voxKWq9DDA=; b=XUqsYLc5gfh0LAKx12R6+M+W4IJZPigGJ/3s6aDE1q7G/hANgybUZ79zcRC8Hz5JOIk0nS D8hdut82Fezbia7vt9WgoI4pnveWsk/WzqpFoCfeFEi5RHp6zXicDUrn4IyDDEPMkA/5FZ 0rmVl2aVUNQdOsrCVsu0lCfijoETxSo= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1714422173; 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=wbbou26awthy0OaHOCg1E2oWXEWL2HTH0voxKWq9DDA=; b=CPyUBR9rDR48D+9U35W2mWlSuIsVW++99Mmknu1ZGKRXGQHZVZAuNFekhbtY2gNDt3Y3FP Ye8CzcQ9vNSO4XAA== 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 EC894139DE; Mon, 29 Apr 2024 20:22:52 +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 A0RqOZwBMGYweQAAD6G6ig (envelope-from ); Mon, 29 Apr 2024 20:22:52 +0000 Message-ID: Date: Mon, 29 Apr 2024 22:22:52 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slub: Fixes freepointer encoding for single free Content-Language: en-US To: Nicolas Bouchinet , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, Xiongwei Song References: <5c34b253-b476-494a-96c9-fe3c95b9b74d@linux.dev> <6f977874-2a18-44ef-b207-9eb0baad9d66@suse.cz> <7074c0b4-62d4-444d-8e59-e23bbbccf9b8@clip-os.org> <83fda406-0340-4b7b-9f02-e9eb41c77f0e@clip-os.org> <73f80886-e390-4320-84dd-68e7cd7e8c62@linux.dev> <10c9a07a-1c6d-4ea7-8c1d-03a7dc5b29d8@clip-os.org> 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+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <10c9a07a-1c6d-4ea7-8c1d-03a7dc5b29d8@clip-os.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Level: X-Spamd-Result: default: False [-3.00 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; XM_UA_NO_VERSION(0.01)[]; MX_GOOD(-0.01)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[12]; FUZZY_BLOCKED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; FREEMAIL_CC(0.00)[linux.com,kernel.org,google.com,lge.com,linux-foundation.org,linux.dev,gmail.com,windriver.com]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.cz:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns] X-Rspamd-Action: no action X-Rspamd-Queue-Id: 12B151F395 X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Score: -3.00 On 4/29/24 6:16 PM, Nicolas Bouchinet wrote: > On 4/29/24 16:52, Chengming Zhou wrote: >> On 2024/4/29 22:32, Nicolas Bouchinet wrote: >>> On 4/29/24 15:35, Chengming Zhou wrote: >>>> On 2024/4/29 20:59, Nicolas Bouchinet wrote: >>>>>> >>>>>> I help maintaining the Linux-Hardened patchset in which we have a slab object canary feature that helps detecting overflows. It is located just after the object freepointer. >>>>> I've tried a patch where the freepointer is avoided but it results in the same bug. It seems that the commit 0f181f9fbea8bc7ea ("mm/slub.c: init_on_free=1 should wipe freelist ptr for bulk allocations") inits the freepointer on allocation if init_on_free is set in order to return a clean initialized object to the caller. >>>>> >>>> Good catch! You may need to change maybe_wipe_obj_freeptr() too, >>>> I haven't tested this, not sure whether it works for you. :) >>>> >>>> diff --git a/mm/slub.c b/mm/slub.c >>>> index 3e33ff900d35..3f250a167cb5 100644 >>>> --- a/mm/slub.c >>>> +++ b/mm/slub.c >>>> @@ -3796,7 +3796,8 @@ static void *__slab_alloc_node(struct kmem_cache *s, >>>>   static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s, >>>>                                                     void *obj) >>>>   { >>>> -       if (unlikely(slab_want_init_on_free(s)) && obj) >>>> +       if (unlikely(slab_want_init_on_free(s)) && obj && >>>> +           !freeptr_outside_object(s)) >>>>                  memset((void *)((char *)kasan_reset_tag(obj) + s->offset), >>>>                          0, sizeof(void *)); >>>>   } >>>> >>>> Thanks! >>> Indeed since check_object() avoids objects for which freepointer is in the object and since val is equal to SLUB_RED_ACTIVE in our specific case it should work. Do you want me to add you as Co-authored ? >>> >> Ok, it's great. Thanks! > > Now I think of it, doesn't it seems a bit odd to only properly > init_on_free object's freepointer only if it's inside the object ? IMHO > it is equally necessary to avoid information leaking about the > freepointer whether it is inside or outside the object. > I think it break the semantic of the commit 0f181f9fbea8bc7ea > ("mm/slub.c: init_on_free=1 should wipe freelist ptr for bulk > allocations") ? Hm, AFAIU, wiping inside object prevents misuse of some buggy kernel code that would allocate and accidentally leak prior content (including the in-object freepointer) somewhere the attacker can read. Now for wiping the freepointer outside the object to be useful it would have assume said leak-prone code to additionally be reading past the allocated object size, i.e. a read buffer overflow. That to me seems to be a much more rare combination, and also in that case such code could also likely read even further past the object, i.e. leak the next object's data? IOW I don't think it buys us much additional security protection in practice? > Thanks. >