From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [PATCH v25 10/12] LRNG - add TRNG support Date: Wed, 20 Nov 2019 21:32:32 +0100 Message-ID: <20191120203232.GB3109949@kroah.com> References: <5390778.VeFRgus4bQ@positron.chronox.de> <19681012.svDddlc5pN@positron.chronox.de> <20191120132918.GA2892197@kroah.com> <1695782.oZ5Vf4nH9s@positron.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <1695782.oZ5Vf4nH9s@positron.chronox.de> Sender: linux-kernel-owner@vger.kernel.org To: Stephan =?iso-8859-1?Q?M=FCller?= Cc: Andy Lutomirski , Arnd Bergmann , Linux Crypto Mailing List , LKML , Linux API , "Eric W. Biederman" , "Alexander E. Patrakov" , "Ahmed S. Darwish" , "Theodore Y. Ts'o" , Willy Tarreau , Matthew Garrett , Vito Caputo , Andreas Dilger , Jan Kara , Ray Strode , William Jon McCann , zhangjs , Florian Weimer , Lennart Poettering , Nicolai Stange P List-Id: linux-api@vger.kernel.org On Wed, Nov 20, 2019 at 08:51:11PM +0100, Stephan Müller wrote: > Am Mittwoch, 20. November 2019, 14:29:18 CET schrieb Greg Kroah-Hartman: > > Hi Greg, > > > On Wed, Nov 20, 2019 at 09:58:35AM +0100, Stephan Müller wrote: > > > Am Dienstag, 19. November 2019, 13:41:50 CET schrieb Greg Kroah-Hartman: > > > > > > Hi Greg, > > > > > > > On Tue, Nov 19, 2019 at 02:07:40AM -0800, Andy Lutomirski wrote: > > > > > > As this would introduce a new device file now, is there a special > > > > > > process that I need to follow or do I need to copy? Which > > > > > > major/minor > > > > > > number should I use? > > > > > > > > > > > > Looking into static const struct memdev devlist[] I see > > > > > > > > > > > > [8] = { "random", 0666, &random_fops, 0 }, > > > > > > [9] = { "urandom", 0666, &urandom_fops, 0 }, > > > > > > > > > > > > Shall a true_random be added here with [10]? > > > > > > > > > > I am not at all an expert on chardevs, but this sounds generally > > > > > reasonable. gregkh is probably the real authority here. > > > > > > > > [10] is the aio char device node, so you better not try to overlap it or > > > > bad things will happen :( > > > > > > Thanks for your insights. > > > > > > Which device minor number could we use? > > > > Get your own dynamic one by using a misc device if you _REALLY_ want to > > add yet-another-char-node-for-random-data. > > > > But I would have thought that we all realize that this is not the way to > > do things. Let's not have "random", "urandom", and "true_random" be > > something we want to totally confuse userspace with, that way is insane. > > > > Please just make the existing userspace api "just work", don't add to > > the mess. > > Thank you, I think we should follow that advise. > > With that and considering Alexander's rightful remark we have a challenge. So, > changing the syscall may not be the right way unless we find a way to restrict > the permissions somehow (capability? LSM? None of that seems to be a good > fit). > > What about providing a /sys file? I.e. adding a file that: > > a) has permissions 440 per default and maybe the ownership of root:root > > b) allow user space to perform a chown/chgrp > > c) only supports reading of data from user space > > But then, how could we provide a common interface for the existing random.c > and the LRNG? > > Or should we use a proc file for that? If yes, I guess it should not be a > sysctl, but a "regular" proc file that should allow a chown(2) operation. On > the other hand, is proc the right place to provide a user space interface for > exporting data to user? No, do not abuse sysfs or procfs for something like this. Use a real syscall please if you really need it. greg k-h