On Thu, Jan 30, 2020 at 07:11:08AM -0700, Jens Axboe wrote: > On 1/30/20 3:26 AM, Christian Brauner wrote: > > On Thu, Jan 30, 2020 at 11:11:58AM +0100, Jann Horn wrote: > >> On Thu, Jan 30, 2020 at 2:08 AM Jens Axboe <axboe@xxxxxxxxx> wrote: > >>> On 1/29/20 10:34 AM, Jens Axboe wrote: > >>>> On 1/29/20 7:59 AM, Jann Horn wrote: > >>>>> On Tue, Jan 28, 2020 at 8:42 PM Jens Axboe <axboe@xxxxxxxxx> wrote: > >>>>>> On 1/28/20 11:04 AM, Jens Axboe wrote: > >>>>>>> On 1/28/20 10:19 AM, Jens Axboe wrote: > >>>>> [...] > >>>>>>>> #1 adds support for registering the personality of the invoking task, > >>>>>>>> and #2 adds support for IORING_OP_USE_CREDS. Right now it's limited to > >>>>>>>> just having one link, it doesn't support a chain of them. > >>>>> [...] > >>>>>> I didn't like it becoming a bit too complicated, both in terms of > >>>>>> implementation and use. And the fact that we'd have to jump through > >>>>>> hoops to make this work for a full chain. > >>>>>> > >>>>>> So I punted and just added sqe->personality and IOSQE_PERSONALITY. > >>>>>> This makes it way easier to use. Same branch: > >>>>>> > >>>>>> https://git.kernel.dk/cgit/linux-block/log/?h=for-5.6/io_uring-vfs-creds > >>>>>> > >>>>>> I'd feel much better with this variant for 5.6. > >>>>> > >>>>> Some general feedback from an inspectability/debuggability perspective: > >>>>> > >>>>> At some point, it might be nice if you could add a .show_fdinfo > >>>>> handler to the io_uring_fops that makes it possible to get a rough > >>>>> overview over the state of the uring by reading /proc/$pid/fdinfo/$fd, > >>>>> just like e.g. eventfd (see eventfd_show_fdinfo()). It might be > >>>>> helpful for debugging to be able to see information about the fixed > >>>>> files and buffers that have been registered. Same for the > >>>>> personalities; that information might also be useful when someone is > >>>>> trying to figure out what privileges a running process actually has. > >>>> > >>>> Agree, that would be a very useful addition. I'll take a look at it. > >>> > >>> Jann, how much info are you looking for? Here's a rough start, just > >>> shows the number of registered files and buffers, and lists the > >>> personalities registered. We could also dump the buffer info for > >>> each of them, and ditto for the files. Not sure how much verbosity > >>> is acceptable in fdinfo? > >> > >> At the moment, I personally am just interested in this from the > >> perspective of being able to audit the state of personalities, to make > >> important information about the security state of processes visible. > >> > >> Good point about verbosity in fdinfo - I'm not sure about that myself either. Afaik, there's no rule here. I would expect that it shouldn't exceed 4096kb just because that is the limit that seems to be enforced for writes to proc files atm; other than that it should be the wild west. The fdinfo files are mostly interesting for anon_inode fds imho and the ones that come to mind right now simply don't have a lot of information to provide: eventfd timerfd seccomp_notify_fd Potentially, the mount fds from David could be extended in the future. (Side note: One thing that comes to mind is that we should probably enforce^Wdocument that all fdinfo files use CamelCase?) Christian
