From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:35646 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726027AbfHOItZ (ORCPT ); Thu, 15 Aug 2019 04:49:25 -0400 Date: Thu, 15 Aug 2019 10:49:21 +0200 From: Greg Kroah-Hartman Subject: Re: [RFC 06/19] ktf: A simple debugfs interface to test results Message-ID: <20190815084921.GE3512@kroah.com> References: <20190813082152.GA17627@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Knut Omang Cc: linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, Shuah Khan , Jonathan Corbet , Masahiro Yamada , Michal Marek , Shreyans Devendra Doshi <0xinfosect0r@gmail.com>, Alan Maguire , Brendan Higgins , Kevin Hilman , Hidenori Yamaji , Frank Rowand , Timothy Bird , Luis Chamberlain , Theodore Ts'o , Daniel Vetter , Stephen Boyd On Wed, Aug 14, 2019 at 07:17:07PM +0200, Knut Omang wrote: > I notice the discussion and your response here: > http://linux-kernel.2935.n7.nabble.com/debugfs-and-module-unloading-td865175.html > I assume that means that protection against module unload while a debugfs file > is open is now safe. It should be, if you set the *owner field of your file_operations properly. Try it and see! > On older kernels, having this code in place is far better than an unprotected > debugfs entry/exit - I have tested it extensively in the past :-) Yes, it seems to work, but again, it really is racy and will fail. Please don't use it. > I perfectly agree with you that reducing the hole for a race condition > is generally a bad idea, but from the above mail thread > it seems that's the only available choice for older kernels? I have no idea, but please, do not use that pattern of code as it is racy in all kernels, from all of time. thanks, greg k-h