linux-kernel - Re: [fuse-devel] fuse_get

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Date:	Fri, 22 May 2015 12:44:35 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Seth Forshee <seth.forshee@...onical.com>
Cc:	Miklos Szeredi <miklos@...redi.hu>, alexey@...nosov.spb.ru,
	Andy Lutomirski <luto@...capital.net>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	fuse-devel <fuse-devel@...ts.sourceforge.net>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [fuse-devel] fuse_get_context() and namespaces

Seth Forshee <seth.forshee@...onical.com> writes:

> On Fri, May 22, 2015 at 04:23:55PM +0200, Miklos Szeredi wrote:
>> On Sat, May 2, 2015 at 5:56 PM,  <alexey@...nosov.spb.ru> 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@...test ~]# lxc-start  -n test-2 /bin/su -
>> > [root@...t-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@...t-2 ~]# python hello.py -f  /mnt/
>> >
>> > On second console:
>> > [root@...t-2 ~]# echo $$
>> > 41
>> > [root@...t-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?

Eric
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