From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (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 A7472135A53; Thu, 26 Sep 2024 08:28:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727339341; cv=none; b=VOxgHnzR5/g4hfBZHQ/eYVHSOTD2XWF/h7SgJJq4jsdOajc8t7u9ZXw1y2ggh3BHowgIpV93H+UH90VSFRXSq7BbJpkuJjvnuCaylUd2J3eD2/eouPpxIujQ8l5YSh6YBkmffNq4scC8X00SrpeZHpXhnEpsnOuqV+kzYn5fZzc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727339341; c=relaxed/simple; bh=cw3hfMpb47IQo5ngCGpgt0Fg5FV4POI3hhBwCbEClRk=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=po4DRefg/HAxGIICobRKL5WG/iimoMf0Z4wo6XlVYpM0VMVGwY4q5Rd3Hm4rew4+6tJOFpv9opJNB9bod8zIw67+XoqS9VTUB07rtqD1aRtYReFA4YvjE39H8HAMecvURpkZHrwwrvw4CJUI8U8L8h+yF69z911fgVxKkrCATNo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.162.112]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4XDmvj1MJmz20pST; Thu, 26 Sep 2024 16:28:33 +0800 (CST) Received: from dggpeml100021.china.huawei.com (unknown [7.185.36.148]) by mail.maildlp.com (Postfix) with ESMTPS id 791CF1400CB; Thu, 26 Sep 2024 16:28:55 +0800 (CST) Received: from [127.0.0.1] (10.174.177.174) by dggpeml100021.china.huawei.com (7.185.36.148) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Thu, 26 Sep 2024 16:28:54 +0800 Message-ID: <142a28f9-5954-47f6-9c0c-26f7c142dbc1@huawei.com> Date: Thu, 26 Sep 2024 16:28:54 +0800 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 1/1] ext4: fix crash on BUG_ON in ext4_alloc_group_tables To: Jan Kara , Alexander Mikhalitsyn CC: , , Andreas Dilger , =?UTF-8?Q?St=C3=A9phane_Graber?= , Christian Brauner , , , , Wesley Hershberger , Yang Erkun References: <20240925143325.518508-1-aleksandr.mikhalitsyn@canonical.com> <20240925143325.518508-2-aleksandr.mikhalitsyn@canonical.com> <20240925155706.zad2euxxuq7h6uja@quack3> Content-Language: en-US From: Baokun Li In-Reply-To: <20240925155706.zad2euxxuq7h6uja@quack3> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml100021.china.huawei.com (7.185.36.148) On 2024/9/25 23:57, Jan Kara wrote: > On Wed 25-09-24 16:33:24, Alexander Mikhalitsyn wrote: >> [ 33.882936] EXT4-fs (dm-5): mounted filesystem 8aaf41b2-6ac0-4fa8-b92b-77d10e1d16ca r/w with ordered data mode. Quota mode: none. >> [ 33.888365] EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks >> [ 33.888740] ------------[ cut here ]------------ >> [ 33.888742] kernel BUG at fs/ext4/resize.c:324! > Ah, I was staring at this for a while before I understood what's going on > (it would be great to explain this in the changelog BTW). As far as I > understand commit 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation > in alloc_flex_gd()") can actually make flex_gd->resize_bg larger than > flexbg_size (for example when ogroup = flexbg_size, ngroup = 2*flexbg_size > - 1) which then confuses things. I think that was not really intended and > instead of fixing up ext4_alloc_group_tables() we should really change > the logic in alloc_flex_gd() to make sure flex_gd->resize_bg never exceeds > flexbg size. Baokun? > > Honza Hi Honza, Your analysis is absolutely correct. It's a bug! Thank you for locating this issue！ An extra 1 should not be added when calculating resize_bg in alloc_flex_gd(). Hi Aleksandr, Could you help test if the following changes work? Thanks, Baokun --- diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c index e04eb08b9060..1f01a7632149 100644 --- a/fs/ext4/resize.c +++ b/fs/ext4/resize.c @@ -253,10 +253,12 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size,         /* Avoid allocating large 'groups' array if not needed */         last_group = o_group | (flex_gd->resize_bg - 1);         if (n_group <= last_group) -               flex_gd->resize_bg = 1 << fls(n_group - o_group + 1); +               flex_gd->resize_bg = 1 << fls(n_group - o_group);         else if (n_group - last_group < flex_gd->resize_bg) -               flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1), +               flex_gd->resize_bg = 1 << max(fls(last_group - o_group),                                               fls(n_group - last_group));         flex_gd->groups = kmalloc_array(flex_gd->resize_bg,                                         sizeof(struct ext4_new_group_data),