gmane.comp.file-systems.fuse.devel

SETATTR and fuse-operations

Christopher Howard — 2012-05-25T19:46:41

Hi. Two questions:

1) I there some way to run a keyword search against the fuse-devel list
archives? All the threads are available from the sourceforge
mailarchive, but I don't see a button or interface for doing a search
for a specific topic. Is this a SF members-only functionality or something?

2) In creating my first FUSE-based file system, I have been following
one of the examples that uses the fuse-operations struct, as opposed to
fuse_lowlevel_ops. However, in trying to test my write function (by
editing a file with a text editor) I keep getting the error

code:
--------
unique: 22, opcode: SETATTR (4), nodeid: 3, insize: 128
   unique: 22, error: -38 (Function not implemented), outsize: 16
--------

But fuse_operations doesn't have a setattr function, only
fuse_lowlevel_ops. Does this mean I have to use fuse_lowlevel_ops?

Re: Current state of the art with inotify-likefunctionality?

JT Olds — 2012-05-25T17:35:43

Will do, thanks.

------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/

Re: Current state of the art with inotify-likefunctionality?

Nikolaus Rath — 2012-05-25T17:08:34

In the low-level API, you can return a timeout value together with the
attributes from the getattr() call. There is probably something like
that in the high level API as well.

But returning wrong attributes, even if only when requested by a
specific PID and with a timeout of zero, seems like inviting trouble to
me. I highly recommend using the access() handler instead, it's a much
cleaner solution.


Best,

   -Nikolaus

Re: Current state of the art with inotify-likefunctionality?

JT Olds — 2012-05-25T16:46:00

Really? How come that stuff is cached? If there's an option to disable
the kernel_cache for file data, is there an option to disable metadata
caching like that? That just seems bad in general for metadata
changing from elsewhere in my network fs.

-JT


------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/

splice capability bits?

Han-Wen Nienhuys — 2012-05-25T16:43:12

Hi there,

I'm working on adding splice support to go-fuse (for writing to the
kernel); Things seem to be working, but it seems the kernel is not
sending me capability bits.

I am getting:

2012/05/25 13:33:10 Dispatch: INIT, NodeId: 0. data: {7.18 Ra=0x20000
EXPORT_SUPPORT,BIG_WRITES,DONT_MASK,ASYNC_READ,FLOCK_LOCKS,ATOMIC_O_TRUNC,POSIX_LOCKS}

should I instead look at the version number to decide whether to splice?

Re: Current state of the art with inotify-likefunctionality?

Nikolaus Rath — 2012-05-25T16:03:01

[...]

The kernel would cache it, and it would appear as +w to every process,
not just your PID.


Best,

   -Nikolaus

Re: Current state of the art with inotify-likefunctionality?

JT Olds — 2012-05-25T15:59:13

Whoops, you're right, I totally hit the wrong button in my email
client. adding back the list.

On Fri, May 25, 2012 at 7:21 AM, Nikolaus Rath <Nikolaus-BTH8mxji4b0< at >public.gmane.org> wrote:

Well, no, the user might do a chmod -w I guess, but as I understand it
there's really no reason I can't return +w in getattr calls to my PID
only.

But that's definitely an important case I'll make sure to write some
unit tests around. Thanks again.

-JT

------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/

Re: mounting: ignore if already mounted

Nikolaus Rath — 2012-05-25T14:05:11


Sven Utcke <sven.utcke-Mmb7MZpHnFY< at >public.gmane.org> writes:

Oh, thanks for the correction. It being the default also explains why I
wasn't able to find any flag for it :-).


Best,

   -Nikolaus

offset to write function

Christopher Howard — 2012-05-24T20:07:35

Regarding the offset parameter passed in to our Fuse write function:
Will this value ever be negative? If it is, is that to be treated as an
error, or does that specify some kind of special address? (E.g., reverse
address from end of data.)

Re: Need to know user for implementing network filesystem security

Sergey Cherepanov — 2012-05-24T19:07:07

 fuse_get_context() works just fine.
Thanks you for explanation!
Sergey

-----Original Message-----
From: Stef Bon [mailto:stefbon-Re5JQEeQqe8AvxtiuMwx3w< at >public.gmane.org]
Sent: Thursday, May 24, 2012 6:45 AM
To: fuse-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f< at >public.gmane.org
Cc: Sergey Cherepanov
Subject: Re: [fuse-devel] Need to know user for implementing network filesystem security

Hi,

I would like to add comment about the access call. When you program this call, it will be used in stead of the standard access rules using uid/gid etc.

This is in the lowlevel interface, I do not know the highlevel one.
And in lowlevel it's

ctx=fuse_req_ctx(req)

and in ctx the uid, gid and pid are set.

Stef Bon

2012/5/23 Fox, Kevin M <kevin.fox-MIjBx5DB8Ok< at >public.gmane.org>:

________________________________

This e-mail and its attachments are intended only for the individual or entity to whom it is addressed and may contain information that is confidential, privileged, inside information, or subject to other restrict

Re: modified hello_ll: setattr error

Han-Wen Nienhuys — 2012-05-24T13:42:21

The attribute you get passed into setattr isn't necessarily a valid
file attribute. Try filling an attr value from scratch.

Re: Need to know user for implementing network filesystem security

Sven Utcke — 2012-05-24T12:32:41

Hello Sergey,


Just to clarify: which part is in FUSE?

Server: This needs to get the user-id from the client, using whatever
        mechanism that particular FS uses.
Client: See the answers you already received.


There used to by a minor problem with ACLs (forgot what it was), but
nothing noticeable in normal operation, just not being 100% POSIX
compatible at some minor point...

Sven

Re: Need to know user for implementing network filesystem security

Stef Bon — 2012-05-24T11:45:04

Hi,

I would like to add comment about the access call. When you program
this call, it will be used in stead of the standard access rules using
uid/gid etc.

This is in the lowlevel interface, I do not know the highlevel one.
And in lowlevel it's

ctx=fuse_req_ctx(req)

and in ctx the uid, gid and pid are set.

Stef Bon

2012/5/23 Fox, Kevin M <kevin.fox< at >pnnl.gov>:

------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
_______________________________________________
fuse-devel mailing list
fuse-devel< at >lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/fuse-devel

modified hello_ll: setattr error

Андрей Гаврилин — 2012-05-24T06:18:55

Hello.

I have modified the example. I have added hello_ll_setattr and
hello_ll_release. It's not read-only now.

$./hello_ll fs -d
$t$ touch fs/hello
touch: closing `fs/hello': Input/output error

Log:
...
unique: 114, opcode: OPEN (14), nodeid: 2, insize: 48
   unique: 114, success, outsize: 32
unique: 115, opcode: FLUSH (25), nodeid: 2, insize: 64
   unique: 115, error: -38 (Function not implemented), outsize: 16
unique: 116, opcode: SETATTR (4), nodeid: 2, insize: 128
   unique: 116, success, outsize: 120
unique: 117, opcode: RELEASE (18), nodeid: 2, insize: 64
   unique: 117, success, outsize: 16
...

Why It doesn't work?


/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA< at >public.gmane.org>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.

  gcc -Wall `pkg-config fuse --cflags --libs` hello_ll.c -o hello_ll
*/

#define FUSE_USE_VERSION 26

#include <fuse_lowlevel.h>
#include <stdio.h>
#include <stdlib.h>

Re: Current state of the art with inotify-likefunctionality?

Stef Bon — 2012-05-23T20:40:59

2012/5/23 JT Olds <jtolds-aCMSg5yP+xoAvxtiuMwx3w< at >public.gmane.org>:

How does your fs knows what has changed??

Stef

------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/

Re: Need to know user for implementing network filesystemsecurity

Fox, Kevin M — 2012-05-23T19:40:41

Hi Sergey

fuse_get_context() -> uid & gid

getpwuid(uid) and getgrnam(gid) may help too.

Kevin
________________________________________
From: Sergey Cherepanov [scherepanov-3jdQX4nv5R1Wk0Htik3J/w< at >public.gmane.org]
Sent: Wednesday, May 23, 2012 10:49 AM
To: 'fuse-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f< at >public.gmane.org'
Subject: [fuse-devel] Need to know user for implementing network filesystem     security

Hi,

We wrote driver for network filesystem using fuse. It works just fine.
I have problem implementing security around access to files on this network filesystem through fuse driver.
This specific filesystem have ACL for each file, not translatable into user:group permission model on linux.
Filesystem will check user permission when opening file, stat file or ls dir. Problem that I do not know what actual user issued request to fuse, this information is not provided.
We are mounting fuse filesystem as root with -o allow_other option, which allow for everybody on box to access fuse mount. It makes fuse l

Need to know user for implementing network filesystemsecurity

Sergey Cherepanov — 2012-05-23T17:49:42

Hi,

We wrote driver for network filesystem using fuse. It works just fine.
I have problem implementing security around access to files on this network filesystem through fuse driver.
This specific filesystem have ACL for each file, not translatable into user:group permission model on linux.
Filesystem will check user permission when opening file, stat file or ls dir. Problem that I do not know what actual user issued request to fuse, this information is not provided.
We are mounting fuse filesystem as root with -o allow_other option, which allow for everybody on box to access fuse mount. It makes fuse look like regular filesystem.
But to implement security, I need to know what user made call to fuse, and pass this information to network filesystem.

Question - is there any way to find who is actual user performing a call?

This problem did not exist originally in fuse, as it was designed to be run as user itself. But as soon as it is possible to share fuse mount with other users, security implementation com

Re: Current state of the art with inotify-likefunctionality?

Nikolaus Rath — 2012-05-23T18:42:46

Some more comment:

I've done something similar like this (file system that accesses its own
mountpoint) for self-testing purposes (but I eventually gave up on it
and just used separate processes). You will need to be extra careful
about locking, especially *outside* of your code. Almost no library ever
assumes that even a simple opendir() call may end up in the same process
again, which can result in very tricky deadlocks if the library does not
release its locks for every system call that accesses the mountpoint.

Another thing to consider is permission checking. Your file system may
be serving directories for which it (or rather, the UID the fs is
running under) has no write rights. For these directories, normal
attempts to create files should fail, but "unmasking" requests should of
course work. This means that you need to implement your own access()
method (which you may have done already), but you also need to
distinguish between ordinary and unmasking requests, e.g. by checking
the PID of the request

Re: Current state of the art with inotify-likefunctionality?

JT Olds — 2012-05-23T17:28:43

Yeah, I guess that's true, huh.

Okay, thanks everyone.

-JT

------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/

Re: Current state of the art with inotify-likefunctionality?

Nikolaus Rath — 2012-05-23T15:06:53

To me this sounds like the best you can possibly do in this situation,
(and I'm not sure why an additional overlay file system would be useful
in either case).

What race conditions are you worried about?

If a local client accesses a file that has been created remotely before
you have unmasked it, the situation is not different from the client
accessing it before the remote change has made it through the network.


Best,

   -Nikolaus

【help】 Why the result shown by 'ls' after fuse mount is '?' coming with such error 'Input/output error'?!

马磊 — 2012-05-23T11:03:02

Hi everyone:
    I  download the example of 'helloword' in fuse.sourceforge.net and then
compile correctly,  the version of fuse on my machine is
[fuse-devel-2.7.4-8.el5]  and os-kernel 2.6.18.8;
but the running info is as follows:


[malei< at >xentest ::Wed May 23::~/test-fuse]$ mkdir mnt2
[malei< at >xentest ::Wed May 23::~/test-fuse]$ ls
hello  #hello.c#  hello.c  mnt  mnt2
[malei< at >xentest ::Wed May 23::~/test-fuse]$ ls -l
total 24
-rwxrwxr-x 1 malei malei 10445 May 23 18:36 hello
-rw-rw-r-- 1 malei malei  3572 May 23 18:33 #hello.c#
-rw-rw-r-- 1 malei malei  3466 May 23 18:34 hello.c
?--------- ? ?     ?         ?            ? mnt
drwxrwxr-x 2 malei malei  4096 May 23 18:43 mnt2
[malei< at >xentest ::Wed May 23::~/test-fuse]$ ./hello ./mnt2
[malei< at >xentest ::Wed May 23::~/test-fuse]$ ls -l
total 20
-rwxrwxr-x 1 malei malei 10445 May 23 18:36 hello
-rw-rw-r-- 1 malei malei  3572 May 23 18:33 #hello.c#
-rw-rw-r-- 1 malei malei  3466 May 23 18:34 hello.c
?--------- ? ?     ?         ?            ? mnt
?--------- ? ?     ?