From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 52F7640D585; Mon, 29 Jun 2026 02:26:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782699977; cv=none; b=CdqljtuuAtEkDaDj3HvByUNqZQl7vP6/dW3Iv9CtB6/M2txS+rQbutD0fg3vcx8PL6dZWfWghske1nIF6vLP1z5lq9nyhIOGuEg5J8D9IyNs77pohHwt8ZMcV4vt1s21GVmIdfzLLRP467Wgqm78CSHxg19aSxSe8+1TKBUPcSg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782699977; c=relaxed/simple; bh=XhgsQytKZ8LjENTZvqWldZQUOZQCsU2oN7N0G7EvCcM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=h928y1IoL6wi0rRoMxuokdhGKotpFsYybagY3f/DqoAq5i1mgVouK6OMg5hnKQs9ax3lLO4RAts9jf3TI0zy6KdNA1EBoifdWnx4Zh2eYcsdINR9UOBjS+FCmKYt3sH0WQpGlJTisTmV132UeN9QNPihpOycWhkPURzFuLwkdGo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=QYiS6laJ; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="QYiS6laJ" Received: from [IPV6:2601:646:8081:7da1:29ce:814c:118a:de3f] ([IPv6:2601:646:8081:7da1:29ce:814c:118a:de3f]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 65T29gd13309161 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Sun, 28 Jun 2026 19:09:42 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 65T29gd13309161 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2026052701; t=1782698984; bh=kv5dJD+a62Qg64IepgQhkySKSNHhTKfnqhs3Kx+EjjY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=QYiS6laJ6bh/Gvvs2qYuXGqIhK5K9kUoaFspoLYFcbNE+I3wVgLg0vVOi9+DzeH3R rO6O6esbn1KCXDDCOf1UVuLiuRjgSlPruj8f5GOLxwHNgb94YMVOSY+A43KGT3FHwH cvVJhSIQmX6mRDi8juy2LqQCpg0D2Ym71EPwKPF6mqxXlNX3XabiNy4QgRlztRA3Gg NMGIfHAan3qEU3IrfeTVpNLTtbVGYRZBrII61mq4WZ3HNLDMgUAYSreMCFSbo3DpQM 59rflZB0TxyCuDmB1Qgqk/M+5uI7b6f88Vg5Mcs3dsnxHckFCn80Nj3aFsnttj/nLE A0B4I8tYzE/SQ== Message-ID: <499a4e15-34a4-421b-946a-c855199fdbf9@zytor.com> Date: Sun, 28 Jun 2026 19:09:37 -0700 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] mm/vmalloc: widen guard region to defeat ENTER-based stack pivot To: Xiang Mei , Pedro Falcato Cc: Kees Cook , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, linux-hardening@vger.kernel.org, Uladzislau Rezki , "Gustavo A . R . Silva" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jennifer Miller , Tiffany Bao , Ruoyu Wang , Adam Doupe , Kyle Zeng , Yan Shoshitaishvili References: <20260626173444.2252041-1-xmei5@asu.edu> Content-Language: en-US, sv-SE From: "H. Peter Anvin" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2026-06-26 13:05, Xiang Mei wrote: > > Thanks for your questions and attention. > > 1) `enter` can do big enough stack pivoting (where we can't find many > `add/sub/adc/sbb rsp, ` doing so) Say what? Using add/sub/lea on %rsp is probably more common than enter, because enter is considered kind of slow. gcc, I believe, will generate "leave" but not "enter" as a result. > 2) `enter` is not rare since we can take part in the instruction. This sentence doesn't parse. -hpa