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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1476C2D0A3 for ; Tue, 3 Nov 2020 16:22:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7297420773 for ; Tue, 3 Nov 2020 16:22:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="H/Q1a6JL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728501AbgKCQW5 (ORCPT ); Tue, 3 Nov 2020 11:22:57 -0500 Received: from mx2.suse.de ([195.135.220.15]:59432 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728465AbgKCQWz (ORCPT ); Tue, 3 Nov 2020 11:22:55 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1604420573; 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: in-reply-to:in-reply-to:references:references; bh=Ncbfu00+z2ljfQkB8wK6dR5MBVW1Agfr/OoexPIcZXM=; b=H/Q1a6JLNwT23WwdE7HZnJM34AH6jqErP2c6racZcPhcitmYRe3Af/FKNh6od17tOEZxbH W8Mcs5c0FkoP3yZLlPC4wc6TmFYhaF9t9/joPJNt5HWfYa+gHBzYN/WOg/go1TqrkrhAy3 VgdmoNAlNLx59T2jSuKrMD8TFcgd01Y= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 406C6ADB3; Tue, 3 Nov 2020 16:22:53 +0000 (UTC) Date: Tue, 3 Nov 2020 17:22:52 +0100 From: Petr Mladek To: Matteo Croce Cc: linux-kernel@vger.kernel.org, Guenter Roeck , Arnd Bergmann , Mike Rapoport , Kees Cook , Pavel Tatashin , Robin Holt Subject: Re: [PATCH v2 2/2] reboot: fix parsing of reboot cpu number Message-ID: <20201103162252.GR20201@alley> References: <20201027133545.58625-1-mcroce@linux.microsoft.com> <20201027133545.58625-3-mcroce@linux.microsoft.com> <20201030143049.GE1602@alley> <20201102110107.GG20201@alley> <20201103142543.GP20201@alley> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 2020-11-03 16:43:59, Matteo Croce wrote: > On Tue, Nov 3, 2020 at 3:25 PM Petr Mladek wrote: > > > > On Tue 2020-11-03 12:43:32, Matteo Croce wrote: > > > On Mon, Nov 2, 2020 at 12:01 PM Petr Mladek wrote: > > > > > > > > On Sun 2020-11-01 02:57:40, Matteo Croce wrote: > > > > > On Fri, Oct 30, 2020 at 3:30 PM Petr Mladek wrote: > > > > > > > > > > > > On Tue 2020-10-27 14:35:45, Matteo Croce wrote: > > > > > > > From: Matteo Croce > > > > > > > > > > > > > > The kernel cmdline reboot= argument allows to specify the CPU used > > > > > > > for rebooting, with the syntax `s####` among the other flags, e.g. > > > > > > > > > > > > > > reboot=soft,s4 > > > > > > > reboot=warm,s31,force > > > > > > > > > > > > > > In the early days the parsing was done with simple_strtoul(), later > > > > > > > deprecated in favor of the safer kstrtoint() which handles overflow. > > > > > > > > > > > > > > But kstrtoint() returns -EINVAL if there are non-digit characters > > > > > > > in a string, so if this flag is not the last given, it's silently > > > > > > > ignored as well as the subsequent ones. > > > > > > > > > > > > > > To fix it, revert the usage of simple_strtoul(), which is no longer > > > > > > > deprecated, and restore the old behaviour. > > > > > > > > > > > > > > While at it, merge two identical code blocks into one. > > > > > > > > > > > > > --- a/kernel/reboot.c > > > > > > > +++ b/kernel/reboot.c > > > > > > > @@ -552,25 +552,19 @@ static int __init reboot_setup(char *str) > > > > > > > > > > > > > > case 's': > > > > > > > { > > > > > > > - int rc; > > > > > > > - > > > > > > > - if (isdigit(*(str+1))) { > > > > > > > - rc = kstrtoint(str+1, 0, &reboot_cpu); > > > > > > > - if (rc) > > > > > > > - return rc; > > > > > > > - if (reboot_cpu >= num_possible_cpus()) { > > > > > > > - reboot_cpu = 0; > > > > > > > - return -ERANGE; > > > > > > > - } > > > > > > > - } else if (str[1] == 'm' && str[2] == 'p' && > > > > > > > - isdigit(*(str+3))) { > > > > > > > - rc = kstrtoint(str+3, 0, &reboot_cpu); > > > > > > > - if (rc) > > > > > > > - return rc; > > > > > > > - if (reboot_cpu >= num_possible_cpus()) { > > > > > > > - reboot_cpu = 0; > > > > > > > > > > > > ^^^^^^ > > > > > > > > > > > > > + int cpu; > > > > > > > + > > > > > > > + /* > > > > > > > + * reboot_cpu is s[mp]#### with #### being the processor > > > > > > > + * to be used for rebooting. Skip 's' or 'smp' prefix. > > > > > > > + */ > > > > > > > + str += str[1] == 'm' && str[2] == 'p' ? 3 : 1; > > > > > > > + > > > > > > > + if (isdigit(str[0])) { > > > > > > > + cpu = simple_strtoul(str, NULL, 0); > > > > > > > + if (cpu >= num_possible_cpus()) > > > > > > > return -ERANGE; > > > > > > > - } > > > > > > > + reboot_cpu = cpu; > > > > > > > > > > > > The original value stays when the new one is out of range. It is > > > > > > small functional change that should get mentioned in the commit > > > > > > message or better fixed separately. > > > > > > > > Ah, I see. From some reason, I assumed that it was defined as > > > > module_param() or core_param(). Then it would be possible to modify > > > > it later via /sys. > > > > > > > > I am sorry for the noise. > > > > > > > > > > Never mind :) > > > > > > So, is this an ack? Or I need to prepare a v3 with the revert as first patch? > > > > Good question ;-) It would be nice to do it the cleaner way but I do > > not resist on it. Feel free to use: > > > > Reviewed-by: Petr Mladek > > > > Now, the question is who would actually push this upstream. These > > patches often go via Andrew Morton. He actually committed both > > changes that are fixed here. > > > > I suggest to resend the patchset with my Reviewed-by and > > Cc: stable@vger.kernel.org lines. And put Andrew and Greg into Cc. > > > > I see that by doing the revert first, makes the patch very small. > It's worth it. Great. > I'm thinking, what should be the right action to do when the supplied > cpu number is too big? > With my patch I stop the parsing, while the previous behavior (other > than setting a wrong cpu number) was to continue parsing other fields. > Maybe I should just continue the loop and continue the parsing? > Maybe with a pr_warn "cpu X exceeds possible cpu number Y" etc. Sounds good to me. Please, make it clear that the error message is printed when parsing reboot= commandline option. For example: pr_err("Ignoring CPU number in reboot= option. CPU X exceeds possible cpu number Y", ...) or something like this. Best Regards, Petr