From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephan =?ISO-8859-1?Q?M=FCller?= Subject: Re: [PATCH v25 10/12] LRNG - add TRNG support Date: Wed, 20 Nov 2019 20:51:11 +0100 Message-ID: <1695782.oZ5Vf4nH9s@positron.chronox.de> References: <5390778.VeFRgus4bQ@positron.chronox.de> <19681012.svDddlc5pN@positron.chronox.de> <20191120132918.GA2892197@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20191120132918.GA2892197@kroah.com> Sender: linux-kernel-owner@vger.kernel.org To: Greg Kroah-Hartman 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 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 M=FCller wrote: > > Am Dienstag, 19. November 2019, 13:41:50 CET schrieb Greg Kroah-Hartman: > >=20 > > Hi Greg, > >=20 > > > 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? > > > > >=20 > > > > > Looking into static const struct memdev devlist[] I see > > > > >=20 > > > > > [8] =3D { "random", 0666, &random_fops, 0 }, > > > > > [9] =3D { "urandom", 0666, &urandom_fops, 0 }, > > > > >=20 > > > > > Shall a true_random be added here with [10]? > > > >=20 > > > > I am not at all an expert on chardevs, but this sounds generally > > > > reasonable. gregkh is probably the real authority here. > > >=20 > > > [10] is the aio char device node, so you better not try to overlap it= or > > > bad things will happen :( > >=20 > > Thanks for your insights. > >=20 > > Which device minor number could we use? >=20 > Get your own dynamic one by using a misc device if you _REALLY_ want to > add yet-another-char-node-for-random-data. >=20 > 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. >=20 > 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,=20 changing the syscall may not be the right way unless we find a way to restr= ict=20 the permissions somehow (capability? LSM? None of that seems to be a good=20 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= =20 and the LRNG? Or should we use a proc file for that? If yes, I guess it should not be a=20 sysctl, but a "regular" proc file that should allow a chown(2) operation. O= n=20 the other hand, is proc the right place to provide a user space interface f= or=20 exporting data to user? Thanks a lot. Ciao Stephan