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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D4A7C4332F for ; Fri, 25 Nov 2022 09:55:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230081AbiKYJzp (ORCPT ); Fri, 25 Nov 2022 04:55:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229901AbiKYJzT (ORCPT ); Fri, 25 Nov 2022 04:55:19 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D1CC14A06A; Fri, 25 Nov 2022 01:52:18 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 98A7E1FD6A; Fri, 25 Nov 2022 09:52:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1669369934; h=from:from:reply-to: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=j5gHcv1jP7rHDv6WjXG8/kTErobBs4ljiKSMXxDZAhA=; b=upDFs7ucUcwcvrOxapflk6090GnTUsxyfpe7ypzG7Rw/r8LOeyJIy1PZ0gp8pKWH0BNVkb 6VmJx3qc3oAVmklDD8qhKrZ7LV+PnBTgTB1MF90M+YPmzvsQ4hx3mAAwHBRa3efFLvRQb6 OgeTGI1KGRk1DeZKcJhHmEtuBm2V8g4= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1669369934; h=from:from:reply-to: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=j5gHcv1jP7rHDv6WjXG8/kTErobBs4ljiKSMXxDZAhA=; b=tLDIqVAy/1R/0p89CwgBqnxXet1EO2WHqlAWHvau5gwhkeHic1UYCZ9rBA9AprOpFj97zg Eu7XC8iadP/J2rCA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 0F6A11361C; Fri, 25 Nov 2022 09:52:14 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id gxRDAU6QgGOEVgAAMHmgww (envelope-from ); Fri, 25 Nov 2022 09:52:14 +0000 Date: Fri, 25 Nov 2022 10:52:12 +0100 From: Andreas Herrmann To: Li Nan Cc: tj@kernel.org, josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yi.zhang@huawei.com Subject: Re: [PATCH -next 1/2] blk-iocost: fix divide by 0 error in calc_lcoefs() Message-ID: References: <20221124140635.695205-1-linan122@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20221124140635.695205-1-linan122@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Nov 24, 2022 at 10:06:34PM +0800, Li Nan wrote: > echo max of u64 to cost.model can cause divide by 0 error. > > # echo 8:0 rbps=18446744073709551615 > /sys/fs/cgroup/io.cost.model > > divide error: 0000 [#1] PREEMPT SMP > RIP: 0010:calc_lcoefs+0x4c/0xc0 > Call Trace: > > ioc_refresh_params+0x2b3/0x4f0 > ioc_cost_model_write+0x3cb/0x4c0 > ? _copy_from_iter+0x6d/0x6c0 > ? kernfs_fop_write_iter+0xfc/0x270 > cgroup_file_write+0xa0/0x200 > kernfs_fop_write_iter+0x17d/0x270 > vfs_write+0x414/0x620 > ksys_write+0x73/0x160 > __x64_sys_write+0x1e/0x30 > do_syscall_64+0x35/0x80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > calc_lcoefs() uses the input value of cost.model in DIV_ROUND_UP_ULL, > overflow would happen if bps plus IOC_PAGE_SIZE is greater than > ULLONG_MAX, it can cause divide by 0 error.I_LCOEF_MAX is introduced to > prevent it. > > Signed-off-by: Li Nan > --- > block/blk-iocost.c | 5 +++++ > 1 file changed, 5 insertions(+) Looks good. Reviewed-by: Andreas Herrmann > diff --git a/block/blk-iocost.c b/block/blk-iocost.c > index f01359906c83..a38a5324bf10 100644 > --- a/block/blk-iocost.c > +++ b/block/blk-iocost.c > @@ -306,6 +306,9 @@ enum { > IOC_PAGE_SIZE = 1 << IOC_PAGE_SHIFT, > IOC_SECT_TO_PAGE_SHIFT = IOC_PAGE_SHIFT - SECTOR_SHIFT, > > + /* avoid overflow */ > + I_LCOEF_MAX = ULLONG_MAX - IOC_PAGE_SIZE, > + > /* if apart further than 16M, consider randio for linear model */ > LCOEF_RANDIO_PAGES = 4096, > }; > @@ -3406,6 +3409,8 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, > goto einval; > if (match_u64(&args[0], &v)) > goto einval; > + if (v > I_LCOEF_MAX) > + goto einval; > u[tok] = v; > user = true; > } > -- > 2.31.1 > -- Regards, Andreas SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nürnberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Martje Boudien Moerman (HRB 36809, AG Nürnberg)