On Mon, 11 Nov 2013 15:33:14 -0500 Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: > > On Nov 11, 2013, at 1:59 PM, Steve Dickson <SteveD@xxxxxxxxxx> wrote: > > > On 11/11/13 13:30, Chuck Lever wrote: > >> > >> On Nov 11, 2013, at 1:06 PM, Steve Dickson <SteveD@xxxxxxxxxx> wrote: > >> > >>> > >>> > >>> On 09/11/13 18:12, Myklebust, Trond wrote: > >>>> One alternative to the above scheme, which I believe that I’ve > >>>> suggested before, is to have a permanent entry in rpc_pipefs > >>>> that rpc.gssd can open and that the kernel can use to detect > >>>> that it is running. If we make it /var/lib/nfs/rpc_pipefs/gssd/clnt00/gssd, > >>>> then AFAICS we don’t need to change nfs-utils at all, since all newer > >>>> versions of rpc.gssd will try to open for read anything of the form > >>>> /var/lib/nfs/rpc_pipefs/*/clntXX/gssd... > >>> > >>> After further review I am going going have to disagree with you on this. > >>> Since all the context is cached on the initial mount the kernel > >>> should be using the call_usermodehelper() to call up to rpc.gssd > >>> to get the context, which means we could put this upcall noise > >>> to bed... forever! :-) > >> > >> Ask Al Viro for his comments on whether the kernel should start > >> gssd (either a daemon or a script). Hint: wear your kevlar underpants. > > I was thinking gssd would become a the gssd-cmd command... Al does not > > like the call_usermodehelper() interface? > > He doesn't have a problem with call_usermodehelper() in general. However, the kernel cannot guarantee security if it has to run a fixed command line. Go ask him to explain. > > > > > >> > >> Have you tried Trond's approach yet? > > Looking into it... But nothing is trivial in that code... > > > >> > >>> I realize this is not going happen overnight, so I would still > >>> like to propose my nfs4_secure_mounts bool patch as bridge > >>> to the new call_usermodehelper() since its the cleanest > >>> solution so far... > >>> > >>> Thoughts? > >> > >> We have workarounds already that work on every kernel since 3.8. > >> > > The one that logs 5 to 20 lines (depending on thins are setup or not) > > per mount? That does work in some environments but no all. ;-) > > When does running rpc.gssd not work? Oohh ooh.. Pick me. Pick me!! I can answer that one. Running rpc.gssd does not work if you are mounting a filesystem using the IP address of the server and that IP address doesn't have a matching hostname anywhere that can be found: In a newly creating minimal kvm install without rpc.gssd running, mount 10.0.2.2:/home /mnt sleeps for 15 seconds then succeeds. If I start rpc.gssd, then the same command takes forever. strace of rpc.gssd shows that it complains about not being able to resolve the host name and "ERROR: failed to read service info". Then it keeps the pipes open but never sends any message on them, so the kernel just keeps on waiting. If I change "fail_keep_client" to "fail_destroy_client", then it closes the pipe and we get the 15 second timeout back. If I change NI_NAMEREQD to 0, then the mount completes instantly. (of course that make serious compromise security so it was just for testing). (Adding an entry to /etc/hosts also gives instant success). I'm hoping that someone who understands this code will suggest something clever so I don't have to dig through all of it ;-) NeilBrown
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