Message-ID: <41F442B0.80900@ngi.it>
Date: Mon, 24 Jan 2005 01:34:56 +0100
From: Alessandro Sappia <a.sappia@ngi.it>
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To: linux-kernel@vger.kernel.org
Subject: chvt issue
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HI all
I was reading vt driver
and I saw
         /*
          * To have permissions to do most of the vt ioctls, we either have
          * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
          */
         perm = 0;
         if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
                 perm = 1;

(lines 382-388 - drivers/char/vt_ioctl.c)

After reading the comment I thinked I can change vt
from one of my own to another one of mine.

so I opened vc/2 and vc/3 and a pts/0
$ w
  01:26:45 up  1:33,  5 users,  load average: 0,84, 0,66, 0,97
USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT
alx      vc/2      01:07   18:51   0.00s  0.00s -bash
alx      vc/3      01:25   48.00s  0.00s  0.00s -bash
alx      :0        23:55   ?xdm?   4:21   0.84s gnome-session
alx      pts/0     01:22    0.00s  0.08s  0.00s w

I went to vc/3 and I did
  $ tty
/dev/vc/3
  $ chvt 2
as i expected I changed my tty to 2
after that I tryied to do the same from pts/0
and

  $ tty
/dev/pts/0
  $ chvt 2
chvt: VT_ACTIVATE: Operation not permitted
  $

After that I went in vc/2
and I did
  $ chvt 12
after that i was watching at my syslog writing messages...
I tryed the same from pts/0
and
  $ chvt 12
Couldnt get a file descriptor referring to the console

So, there are some things I couldn't get about virtual terminal ioctls 
and fd...
please note that use chvt having CAP_SYS_TTY_CONFIG (root) works fine.

Is it possible to change terminal from an unprivileged user ?

THanks in advance
for the time you'll spend answering me.

Alessandro
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