From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) (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 DD53F13AF8; Sat, 27 Jan 2024 10:44:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706352277; cv=none; b=OSIyQNcG0dVAUhcKOVJ8heFPkovEdIIshO7wyquXW+2OnePHls4c1bKbVfUndEFEI1/GzBxODHfKNr44ndB6yw8dbByY9dIS1xxtcmN1bO+pjgCDEk6kjm+wYKBsQiuK3XgWDgdCuTP+3nhnFboidQ6CpfVvejyOAcG/UyDley0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706352277; c=relaxed/simple; bh=Z0OLXXueoKiA/wGx60KBXxyU+VA6Uzmv+t+EL7bXNe4=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=QvPDhN9EIoWg1J3qYGVTX7/S0/4B4PieLhiFSqeIeowkJJf+alVDxS+OJ0KMaNng3Kmf3ym1UWcH0262F7YtjH98i8kAK1l2BwHZrZOMIF3gpivX5SS9UYaatKxZPh3ICnREAmHIJzIgzShSKTtJBBtkeG9JxdXix7Ga1jNMv6k= 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=45.249.212.189 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 [172.19.162.254]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4TMWPf6K9jzNlbd; Sat, 27 Jan 2024 18:43:34 +0800 (CST) Received: from dggpeml500021.china.huawei.com (unknown [7.185.36.21]) by mail.maildlp.com (Postfix) with ESMTPS id F10CC18001C; Sat, 27 Jan 2024 18:44:30 +0800 (CST) Received: from [10.174.177.174] (10.174.177.174) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Sat, 27 Jan 2024 18:44:30 +0800 Message-ID: Date: Sat, 27 Jan 2024 18:44:29 +0800 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.2 Subject: Re: [PATCH 1/7] ext4: avoid overflow when setting values via sysfs To: Alexey Dobriyan CC: , , , , , , , , , , Baokun Li References: <1da0649d-812f-4dee-9c1b-af567afa2e46@p183> Content-Language: en-US From: Baokun Li In-Reply-To: <1da0649d-812f-4dee-9c1b-af567afa2e46@p183> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpeml500021.china.huawei.com (7.185.36.21) On 2024/1/27 17:44, Alexey Dobriyan wrote: > Baokun Li wrote: > >> @@ -463,6 +463,8 @@ static ssize_t ext4_attr_store(struct kobject *kobj, >> ret = kstrtoul(skip_spaces(buf), 0, &t); >> if (ret) >> return ret; >> + if (t != (unsigned int)t) >> + return -EINVAL; > kstrto*() interface has variants for all standard types. > It should be changed to kstrtou32() or kstrtouint(); > > If you check if kstrto*() result fits into another type, > you're probably doing it wrong. Thanks for your comments! The reason for not using those helper functions directly is as follows: 1）Those functions are also based on kstrtoull() wrappers, and if we use kstrtou32() or kstrtouint(), we'd need to declare u32 t or int t, which would leave us with a lot of declared but unused variables, and an unsigned long t would be enough to cover our scenario. 2）Moreover, the actual range of a uint type sysfs interface may not be 0-UINT_MAX, but 0-INT_MAX or 0-s_clusters_per_group, and we need to limit the range of the variable according to the actual meaning of the variable. 3）In addition, by declaring only an unsigned long type and then uniformly parsing it with kstrtoul() and then restricting the range of the variable according to the actual meaning of the variable, we can reduce a lot of repetitive code. >> if (a->attr_ptr == ptr_ext4_super_block_offset) >> *((__le32 *) ptr) = cpu_to_le32(t); -- With Best Regards, Baokun Li .