From mboxrd@z Thu Jan 1 00:00:00 1970 From: Seth Forshee Subject: Re: [fuse-devel] fuse_get_context() and namespaces Date: Fri, 22 May 2015 13:59:32 -0500 Message-ID: <20150522185932.GC126334@ubuntu-hedt> References: <20150331011423.GC13083@unsen.q53.spb.ru> <20150401155515.GA2994@unsen.q53.spb.ru> <20150502155623.GD13083@unsen.q53.spb.ru> <20150522144702.GA126334@ubuntu-hedt> <87iobk4id8.fsf@x220.int.ebiederm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Miklos Szeredi , alexey@kurnosov.spb.ru, Andy Lutomirski , Serge Hallyn , fuse-devel , Linux-Fsdevel , Kernel Mailing List To: "Eric W. Biederman" Return-path: Content-Disposition: inline In-Reply-To: <87iobk4id8.fsf@x220.int.ebiederm.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Fri, May 22, 2015 at 12:44:35PM -0500, Eric W. Biederman wrote: > Seth Forshee writes: > > > On Fri, May 22, 2015 at 04:23:55PM +0200, Miklos Szeredi wrote: > >> On Sat, May 2, 2015 at 5:56 PM, wrote: > >> > > >> > 3.10.0-229 form Scientific Linux and native 4.0.1-1 (from elrepo). > >> > SL 7.1 on the host and SL 6.6 on the LXC guest. At least in 3.10 > >> > the 499dcf2024092e5cce41d05599a5b51d1f92031a is present. > >> > Steps to reproduce: > >> > > >> > On first console: > >> > [root@sl7test ~]# lxc-start -n test-2 /bin/su - > >> > [root@test-2 ~]# diff -u hello.py /usr/share/doc/fuse-python-0.2.1/example/hello.py > >> > --- hello.py 2015-05-02 11:12:13.963093580 -0400 > >> > +++ /usr/share/doc/fuse-python-0.2.1/example/hello.py 2010-04-14 18:29:21.000000000 -0400 > >> > @@ -41,8 +41,6 @@ > >> > class HelloFS(Fuse): > >> > > >> > def getattr(self, path): > >> > - dic = Fuse.GetContext(self) > >> > - print dic > >> > st = MyStat() > >> > if path == '/': > >> > st.st_mode = stat.S_IFDIR | 0755 > >> > [root@test-2 ~]# python hello.py -f /mnt/ > >> > > >> > On second console: > >> > [root@test-2 ~]# echo $$ > >> > 41 > >> > [root@test-2 ~]# ls /mnt/ > >> > hello > >> > > >> > Output of first console: > >> > {'gid': 0, 'pid': 12083, 'uid': 0} > >> > >> Thanks. > >> > >> Digging in mailbox... There was a thread last year about adding > >> support for running fuse daemon in a container: > >> > >> http://thread.gmane.org/gmane.linux.kernel/1811658 > >> > >> Not sure what happened, but no updated patches have been posted or > >> maybe I just missed them. > > > > I haven't sent updated patches in a while. I still intend to, but I > > shifted focus to first getting general support for mounts from user > > namespaces into the vfs (which will give a clearer direction for some of > > the concerns raised about the fuse patches). > > > > All of this code is available in the userns-mounts branch of > > git://kernel.ubuntu.com/sforshee/linux.git, and I don't think the fuse > > patches actually depend on any of the stuff that precedes them. I'm > > planning to start submitting some of the earlier patches from that > > branch soon, and eventually get back to resubmitting the fuse patches. > > > > This is about pid namespaces though, and the fuse pid namespace patch > > from that series (see below) should be more or less independent of the > > rest of the patches. Potentially that could be merged separately from > > the user namespae stuff. > > [snip] > > > @@ -2076,7 +2077,15 @@ static int convert_fuse_file_lock(const struct fuse_file_lock *ffl, > > > > fl->fl_start = ffl->start; > > fl->fl_end = ffl->end; > > - fl->fl_pid = ffl->pid; > > + > > + /* > > + * Convert pid into the connection's pid namespace. If the > > + * pid does not map into the namespace fl_pid will get set > > + * to 0. > > + */ > > + rcu_read_lock(); > > + fl->fl_pid = pid_vnr(find_pid_ns(ffl->pid, fc->pid_ns)); > > + rcu_read_unlock(); > > Scratches my head. This looks wrong. > > I would have expected pid_nr_ns. Am I missing something reading this > patch quickly? Here we're in the context of a F_GETLK operation. We've requested the lock information from the fuse process, and ffl->pid is the pid number in that process's pid namespace so it needs to be translated into current's namespace. First we have to look up the struct pid, then pid_vnr is just a wrapper for pid_nr_ns in the current pid namespace: pid_t pid_vnr(struct pid *pid) { return pid_nr_ns(pid, task_active_pid_ns(current)); } Oh, but the comment is wrong, so maybe that's what confused you. s/connection/caller/ there and it should make more sense. Seth