From mboxrd@z Thu Jan 1 00:00:00 1970 From: James.Bottomley@suse.de (James Bottomley) Date: Tue, 15 Mar 2011 12:32:31 -0400 Subject: [Security] [PATCH 00/20] world-writable files in sysfs and debugfs In-Reply-To: <20110315160804.GA3380@albatros> References: <1300155965.5665.15.camel@mulgrave.site> <20110315030956.GA2234@kroah.com> <1300189828.4017.2.camel@mulgrave.site> <20110315160804.GA3380@albatros> Message-ID: <1300206751.11313.3.camel@mulgrave.site> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 2011-03-15 at 19:08 +0300, Vasiliy Kulikov wrote: > On Tue, Mar 15, 2011 at 07:50 -0400, James Bottomley wrote: > > 1. Did anyone actually check for capabilities before assuming world > > writeable files were wrong? > > I didn't check all these files as I haven't got these hardware :-) You don't need the hardware to check ... the question becomes is a capabilities test sitting in the implementation or not. > But > as I can "chmod a+w" all sysfs files on my machine and they all become > sensible to nonroot writes, I suppose there is nothing preventing > nonroot users from writing to these buggy sysfs files. As you can see, > there are no capable() checks in these drivers in open() or write(). > > > 2. Even if there aren't any capabilities checks in the implementing > > routines, should there be (are we going the separated > > capabilities route vs the monolithic root route)? > > IMO, In any case old good DAC security model must not be obsoleted just > because someone thinks that MAC or anything else is more convenient for > him. If sysfs is implemented via filesystem then it must support POSIX > permissions semantic. MAC is very good in _some_ cases, but not instead > of DAC. Um, I'm not sure that's even an issue. capabilities have CAP_ADMIN which is precisely the same check as owner == root. We use this a lot because ioctls ignore the standard unix DAC model. James