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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 294CFC43219 for ; Wed, 1 May 2019 09:53:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ECE0520835 for ; Wed, 1 May 2019 09:53:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726253AbfEAJx4 convert rfc822-to-8bit (ORCPT ); Wed, 1 May 2019 05:53:56 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:57095 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725959AbfEAJx4 (ORCPT ); Wed, 1 May 2019 05:53:56 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-221-1XAtXxknNhyca-4tma7EeQ-1; Wed, 01 May 2019 10:53:53 +0100 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b::d117) by AcuMS.aculab.com (fd9f:af1c:a25b::d117) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Wed, 1 May 2019 10:53:52 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Wed, 1 May 2019 10:53:52 +0100 From: David Laight To: "linux-kernel@vger.kernel.org" Subject: Upper limit for sysctl fs.file-max Thread-Topic: Upper limit for sysctl fs.file-max Thread-Index: AdUAA8ivBxEHYWXCQH+fjE5WlM/5oQ== Date: Wed, 1 May 2019 09:53:52 +0000 Message-ID: Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: 1XAtXxknNhyca-4tma7EeQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The normal default for fs.file-max (the maximum number of file structures) is 1/10240th of the available memory. However it seems to be possible to set fs.file-max to any value up to 2^64-1. While all 'large' values are effectively the same this seems rather excessive here. Problems arrive when any shell scripts (or anything else that only really has signed 64bit numbers) try to process values above 2^63-1 as these cause errors and/or other unexpected actions. ISTM that the values of a lot of sysctl parameters should be limited to avoid such problems. We've hit this because something is awry in the 5.0 kernel in ubuntu 19.04. Booting the failing userspace with a 5.1-rcx kernel is ok. Nothing looks wrong with the object code for the function that sets the default, and the last thing it does is divide by 10 so it is difficult for it to generate -1. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)