linux-kernel - Re: [v3][PATCH 5/5] Merge code for single and multiple-instance mounts

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Date:	Thu, 07 May 2009 18:33:19 -0400
From:	Eric Paris <eparis@...hat.com>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Eric Paris <eparis@...isplace.org>, Christoph Hellwig <hch@....de>,
	Andrew Morton <akpm@...l.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, serue@...ibm.com,
	hpa@...or.com, sukadev@...ibm.com, linux-kernel@...r.kernel.org,
	jbacik@...hat.com
Subject: Re: [v3][PATCH 5/5] Merge code for single and multiple-instance
 mounts

On Thu, 2009-05-07 at 14:24 -0700, Sukadev Bhattiprolu wrote: 
> Eric Paris [eparis@...isplace.org] wrote:
> | On Sat, Mar 7, 2009 at 2:12 PM, Sukadev Bhattiprolu
> | <sukadev@...ux.vnet.ibm.com> wrote:
> | >
> | > From: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
> | > Subject: [v3][PATCH 5/5] Merge code for single and multiple-instance mounts
> | 
> | I just tried to load the linux-next kernel on F11 and ran into a
> | problem.  X started, I could log in, I could start programs like
> | firefox and evolution, but not gnome-terminal.  It would just flash
> | and disappear.  Running xterm resulted in a window, that I could type
> | in, but it wasn't a shell.  It didn't do anything.
> | 
> | I switched to vt2 set the display to my X session and tried to run
> | xterm.  It said something about a permission being denied, so I
> | decided to strace it.  I saw EACCESS returning from calls dealing with
> | /dev/pts/0.  This lead me to git bisect start fs/devpts from the
> | latest in linux-next as bad and 2.6.29 as good.  Couple interations
> | later and I find that this commit (1bd7903560f1f7) breaks
> | gnome-terminal xterm!
> 
> Interesting :-) -EACCESS makes me suspect that maybe 'mode' 'uid' or 'gid'
> mount options are wrong. Of course we would still need to understand if/
> why this patch changes the settings.
> 
> Can you paste the output of following commands: (both in success and failure
> cases).
> 
> 	$ grep devpts /proc/mounts

Success: devpts /dev/pts devpts rw,relatime,mode=600,ptmxmode=000 0 0
Failure: devpts /dev/pts devpts rw,seclabel,relatime,mode=000,ptmxmode=000 0 0

> 	$ ls -al /dev/pts
Success:
[root@...p231-142 ~]# ls -al /dev/pts
total 0
drwxr-xr-x.  2 root  root       0 2009-05-07 16:04 .
drwxr-xr-x. 20 root  root    5300 2009-05-07 18:13 ..
crw--w----.  1 paris paris 136, 0 2009-05-07 18:17 0
crw--w----.  1 paris paris 136, 1 2009-05-07 16:07 1
crw--w----.  1 paris paris 136, 2 2009-05-07 18:13 2
crw--w----.  1 paris paris 136, 3 2009-05-07 18:17 3
c---------.  1 root  root    5, 2 2009-05-07 16:04 ptmx 

Failure:
[root@...p231-142 ~]# ls -al /dev/pts
total 0
drwxr-xr-x.  2 root  root       0 2009-05-07 18:22 .
drwxr-xr-x. 20 root  root    5460 2009-05-07 18:28 ..
c---------.  1 root  root    5, 2 2009-05-07 18:22 ptmx

> 	$ stat /dev/ptmx


Failure:
  File: `/dev/ptmx'
  Size: 0               Blocks: 0          IO Block: 4096   character special file
Device: eh/14d  Inode: 704         Links: 1     Device type: 5,2
Access: (0666/crw-rw-rw-)  Uid: (    0/    root)   Gid: (    5/     tty)
Access: 2009-05-07 18:23:20.695621624 -0400
Modify: 2009-05-07 18:22:25.460004885 -0400
Change: 2009-05-07 18:22:31.911129737 -0400

> 
> Also, is CONFIG_DEVPTS_MULTIPLE_INSTANCES set in your .config ?

CONFIG_DEVPTS_MULTIPLE_INSTANCES=y

> With this patch, does gnome-terminal run when logged in as root ?

gnome-terminal did not, but xterm did appear in my window as root.  I
assumed it was just some gnomism to not let me launch a root
gnome-terminal inside the user owned X session.


I unmounted /dev/pts and remounted it with mode=600 and it works now!

So something about this patch caused it to change from being mounted 600
to 000.....

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