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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5ADF0CD98D2 for ; Sat, 13 Jun 2026 06:07:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 83D8F6B0005; Sat, 13 Jun 2026 02:07:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7EED16B008A; Sat, 13 Jun 2026 02:07:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 705006B008C; Sat, 13 Jun 2026 02:07:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 634A66B0005 for ; Sat, 13 Jun 2026 02:07:03 -0400 (EDT) Received: from smtpin06.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id D3067120357 for ; Sat, 13 Jun 2026 06:07:02 +0000 (UTC) X-FDA: 84873856284.06.FB18F6D Received: from out-188.mta1.migadu.com (out-188.mta1.migadu.com [95.215.58.188]) by imf05.hostedemail.com (Postfix) with ESMTP id ED8A3100003 for ; Sat, 13 Jun 2026 06:07:00 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=M880zC7u; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf05.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.188 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1781330821; 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=Syw7ULXdB5dW8ZcIfM7qGgtXBrTWdNGVXAYsbJq7l1s=; b=eixVALSKuuwKLJZGZOkCE77T1ZOPZEo4SDq/tYpdkhuNwzkOKGi595EvRMtueM07+q4xJm nUB/6aRwtw+sv3kJblcXDoh9ECde7T7mWPeTHYy5f2zl5h3S6iQ2E51v0HNSgATzlpw9NE Qc7xAZrsxtfsrjyoRRGRBsgNcAX8VOg= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=M880zC7u; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf05.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.188 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1781330821; b=033bpHq49R+ZeAnkHuZCXtgd/BxJ5IuRoMlrh2TS02bbeWt/vq0vYfqRhQG4HHPdUtqzfx 7BxvOYn9KxGNaDJINCbt1lHHeZnMN454GcuUv/fsgGKMcmxR7mUV3vf+e0K5SfDfZ2w2IG OgB+Ux1IFPIxg8eRblIvBiK+iBKXmyg= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781330818; h=from:from: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; bh=Syw7ULXdB5dW8ZcIfM7qGgtXBrTWdNGVXAYsbJq7l1s=; b=M880zC7u2byTFN+N4Gq3ygEGJV6uJ/y323l98Uq2VwiDsDKwwbe3KSZIsE6fswnZXAIDQM ncME5PeWmLbP9V5sIdSHUE8XEIhJI9+8OEhIAu5FhcUJagvyZNVQOVT5s3ZSRIrP6Q0Swr Ebk61m5Zsus12EN++gCjPlzL6R/lrYY= From: Lance Yang To: dev.jain@arm.com Cc: ryabinin.a.a@gmail.com, akpm@linux-foundation.org, corbet@lwn.net, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, workflows@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, kaleshsingh@google.com, 21cnbao@gmail.com, david@kernel.org, will@kernel.org, catalin.marinas@arm.com, Lance Yang Subject: Re: [RFC PATCH 0/2] kasan: hw_tags: Add option to tag only at allocation time Date: Sat, 13 Jun 2026 14:06:37 +0800 Message-Id: <20260613060637.40039-1-lance.yang@linux.dev> In-Reply-To: <20260612044425.763060-1-dev.jain@arm.com> References: <20260612044425.763060-1-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: 9t17cgahnbjc9dooghjkt8ihir3496qt X-Rspamd-Queue-Id: ED8A3100003 X-HE-Tag: 1781330820-380841 X-HE-Meta: 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 flVjkTUA KmsPTrh8ObLbFJKNjdv0AZRNIXR1cD3r5Y2EByErghHKPPwG5tgZvTzVlRMp0U46wKc3ZZm56iixAs6IDsD2DK5Ox4i0tAVcxunRs8U+Ufh3U2NX2XeLZiGhOCexhdPh+UAAXSOePbIH+bNvQm2za0SKeKkNz0B5ZNf/ikgbUOhqouKAffraSvjX2jY4RBA7W8eG02R34GudHzRZGQWJWB816h4kU62fgoDs3wkpjAxfYMFyqf9xE91/ZiBad6/aZDSIM1qTQhbpMlWRCXRFMcPl91ECPq76FfzH5Ushnn2wBDp5aDysVne1AOIpenCcplf1eBlGrPPVgdZs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jun 12, 2026 at 04:44:22AM +0000, Dev Jain wrote: >Introduce a boot option to tag only at allocation time of the objects. This >reduces KASAN MTE overhead, the tradeoff being reduced ability of >catching bugs. > >Now, when a memory object will be freed, it will retain the random tag it >had at allocation time. This compromises on catching UAF bugs, till the >time the object is not reallocated, at which point it will have a new >random tag. > >Hence, not catching "use-after-free-before-reallocation" and not catching >"double-free" will be the compromise for reduced KASAN overhead. Hmm ... do we also need to teach the KASAN KUnit tests about this mode? With kasan.tag_only_on_alloc=on, free-time poisoning is skipped, so some UAF and double-free reports are skipped on purpose, but the tests still expect them :) Cheers, Lance