From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 5D8B039EF0B; Fri, 10 Apr 2026 18:37:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775846232; cv=none; b=sXxK/w9Piuzh4AOzO6o0KB/H69/P/i2iFSBMKrdgiUM41Fxb7dE5DeWB8P7tpt8Chvr1ZOy4mPFtuZbsePUew4A+bN60iLXgsu8JKRugtYeSJdRFUvTm8v5gmSD8QQXfyhTdrU0IRuN+Btf1cFhJ2R8WiX4qMsnmouoyh9LdjmI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775846232; c=relaxed/simple; bh=er8Lk2y7reXP4++X5Sc35l4FKj9mHmvIFq8jXXRDfFQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qoyTsbzGAqHTfxoz7X5AEnn4PAhJbzLoPMQD3GDIHZ30zbCPqfpFT9Acm/p3NmprwUqXAABZs7A70w/qftHTTrjcWY2ID7KrJKgNKf4Ys0a+Q0g6Soe+uUbuVFob79xHkROwxlVMmURcggUMFjHZRDxO7HOD5S3pKo+PokZQzkg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=QMQvUPjg; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="QMQvUPjg" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7006C47E0; Fri, 10 Apr 2026 11:36:59 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D245E3F632; Fri, 10 Apr 2026 11:37:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1775846225; bh=er8Lk2y7reXP4++X5Sc35l4FKj9mHmvIFq8jXXRDfFQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QMQvUPjgfeyLuB/485mMx/3GHF1ky2aQNxTM1JIHTQ5ql0H5z4anq3Y+ovhp6rg1/ CafKVxr6xm/rkQGOM2K4SrZBnmR3oTFtS2b/LojZ/SneD3d4ANbWFlM86a/4uEJTjm thNXSFKO8POWl4qlbgcvzJVEcKvjrmJnlN1/u5Go= Date: Fri, 10 Apr 2026 19:36:58 +0100 From: Catalin Marinas To: Muhammad Usama Anjum Cc: Arnd Bergmann , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Kees Cook , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Uladzislau Rezki , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrey Konovalov , Marco Elver , Vincenzo Frascino , Peter Collingbourne , Will Deacon , Ryan.Roberts@arm.com, david.hildenbrand@arm.com Subject: Re: [PATCH v2 2/3] kasan: skip HW tagging for all kernel thread stacks Message-ID: References: <20260324132631.482520-1-usama.anjum@arm.com> <20260324132631.482520-3-usama.anjum@arm.com> Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Apr 10, 2026 at 07:32:23PM +0100, Catalin Marinas wrote: > What the original approach might help with is use-after-realloc in case > we had a tagged pointer in a past life of a page and it still works now. > Oh well, that's I guess for other types of hardening to address like > delayed reallocation. Another thought (for a separate series) - we could try to map the stack as Untagged (unless stack tagging is enabled; needs compiler instrumentation) and enable canonical tag checking (newer addition to MTE). This way, any stray tagged pointer won't work on the stack since it needs a 0xf tag (canonical). -- Catalin