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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 701EFCD98D2 for ; Sat, 13 Jun 2026 06:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Syw7ULXdB5dW8ZcIfM7qGgtXBrTWdNGVXAYsbJq7l1s=; b=CAPS005jv1WKYGEzUsrQM2m/2w xoZePSftTwue/YKnhVy3NrOdIxF1KeYo5PmNP+VYq8am41/bA5y9pSfRTUBpb8gB0PW0NT7zcknrZ z6skTw0ZJ+/yJmyTif6sxd7TFQoCScIf8zY0+IB/n9MHt0E6jG5U7qx7l+Phc2BbpArArFhPDiJzI orSBp8kbdRhrUPaa+keeImxgox5IebZYPhCeej0dGpk8cftnmARHilWCaPpSyAy10PLQphHsTMq92 iHkOnlyJzRvpmI/SdnDZK3DZ/wCbr2/o0WLZ0vhgAy8s3zfivvE/+hRy12383Lp88JzYRu6r6Svr/ 99SDzf7w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wYHWS-0000000BzGM-3Mxg; Sat, 13 Jun 2026 06:07:12 +0000 Received: from out-186.mta1.migadu.com ([2001:41d0:203:375::ba]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wYHWL-0000000BzFg-3ABz for linux-arm-kernel@lists.infradead.org; Sat, 13 Jun 2026 06:07:11 +0000 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260612_230708_118070_93C352B0 X-CRM114-Status: UNSURE ( 7.47 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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