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]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8129C433F5 for ; Wed, 23 Feb 2022 08:35:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 570A88D0002; Wed, 23 Feb 2022 03:35:46 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 520838D0001; Wed, 23 Feb 2022 03:35:46 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 40E938D0002; Wed, 23 Feb 2022 03:35:46 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0061.hostedemail.com [216.40.44.61]) by kanga.kvack.org (Postfix) with ESMTP id 322968D0001 for ; Wed, 23 Feb 2022 03:35:46 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id DCB2218194D62 for ; Wed, 23 Feb 2022 08:35:45 +0000 (UTC) X-FDA: 79173386250.24.BD32A11 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf27.hostedemail.com (Postfix) with ESMTP id 3E9DE40005 for ; Wed, 23 Feb 2022 08:35:45 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id EF53C21138; Wed, 23 Feb 2022 08:35:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1645605343; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=02cl20i2Gq77a/yxNfOu7oH0En+DuGmAqR7Fchia8K0=; b=UzvwPXkBd9GmrXx/Os/RtO2ydkyecHnJjjKFIucWXNY6ETW01xsThg3eHy0msviPF3aR5D eg+jkY3WePRE4zvxvtOfACRlph9JnzkS0/7zkidwE3BP8x513apnBzIpDMmdzbikRHUiQb N7IEkNCLlAqd84+mqfIgEujKsDkATNE= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id AEC6FA3B81; Wed, 23 Feb 2022 08:35:43 +0000 (UTC) Date: Wed, 23 Feb 2022 09:35:43 +0100 From: Michal Hocko To: Dan Carpenter Cc: "Schaufler, Casey" , Mike Kravetz , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Baolin Wang , Zhenguo Yao , Liu Yuntao , Andrew Morton , "casey@schaufler-ca.com" Subject: Re: [PATCH v2] hugetlb: clean up potential spectre issue warnings Message-ID: References: <20220218212946.35441-1-mike.kravetz@oracle.com> <26565cd7-01b0-197c-6ce9-af92f5bc8563@oracle.com> <20220222163610.GG3943@kadam> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220222163610.GG3943@kadam> X-Rspam-User: Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=UzvwPXkB; spf=pass (imf27.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 3E9DE40005 X-Stat-Signature: nnjmbsuitie1wiw34bppzqxtpbne9usq X-HE-Tag: 1645605345-260817 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 22-02-22 19:36:10, Dan Carpenter wrote: > On Tue, Feb 22, 2022 at 04:15:45PM +0000, Schaufler, Casey wrote: > > > -----Original Message----- > > > From: Michal Hocko > > > Sent: Monday, February 21, 2022 11:48 PM > > > To: Mike Kravetz > > > Cc: linux-mm@kvack.org; linux-kernel@vger.kernel.org; Baolin Wang > > > ; Zhenguo Yao > > > ; Liu Yuntao ; Dan > > > Carpenter ; Andrew Morton > > foundation.org> > > > Subject: Re: [PATCH v2] hugetlb: clean up potential spectre issue warnings > > > > > > On Mon 21-02-22 12:24:25, Mike Kravetz wrote: > > > > On 2/21/22 00:42, Michal Hocko wrote: > > > > > On Fri 18-02-22 13:29:46, Mike Kravetz wrote: > > > > > [...] > > > > >> @@ -4161,7 +4162,7 @@ static int __init hugepages_setup(char *s) > > > > >> } > > > > >> if (tmp >= nr_online_nodes) > > > > >> goto invalid; > > > > >> - node = tmp; > > > > >> + node = array_index_nospec(tmp, nr_online_nodes); > > > > >> p += count + 1; > > > > >> /* Parse hugepages */ > > > > >> if (sscanf(p, "%lu%n", &tmp, &count) != 1) > > > > >> @@ -6889,9 +6890,9 @@ static int __init > > > cmdline_parse_hugetlb_cma(char *p) > > > > >> break; > > > > >> > > > > >> if (s[count] == ':') { > > > > >> - nid = tmp; > > > > >> - if (nid < 0 || nid >= MAX_NUMNODES) > > > > >> + if (tmp >= MAX_NUMNODES) > > > > >> break; > > > > >> + nid = array_index_nospec(tmp, MAX_NUMNODES); > > > > >> > > > > >> s += count + 1; > > > > >> tmp = memparse(s, &s); > > > > > > > > > > This is an early boot code, how is this supposed to be used as a side > > > > > channel? > > > > > > > > I do not have an evil hacker mind, but I can not think of a way this one time > > > > use of a user specified index could be an issue. It does add noise to the > > > > BUILD REGRESSION emails sent to Andrew. > > > > > > Maybe Smack can be taught to ignore __init and other early boot > > > functions. > > > > Why is Smack getting called out? The relationship is not obvious. > > > > He meant Smatch. It's a really common mistake that I did not anticipate > in 2002. Right. My bad. > I can probably silence the spectre warnings for __init functions. TBH, > I don't really understand spectre at all so I mostly ignore those > warnings. :/ AFAIU the spectre gadget would need to be called repeatedly to be usable for a side channel attack. I might be really missing some scenario but to me it seems that __init functions cannot really be used for that. -- Michal Hocko SUSE Labs