Groups > comp.os.linux.development.system > #469

Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--'

Newsgroups	comp.os.linux.development.system
Date	2012-10-02 10:46 -0700
References	<20de89c1-dcb3-42b2-b281-d22af2035db5@googlegroups.com> <87ehlh9d99.fsf@araminta.anjou.terraraq.org.uk> <c8cf57cb-5078-4996-9cea-c36d36c98348@googlegroups.com> <k4f7du$ind$1@dont-email.me>
Message-ID	<45b5a20b-9fed-4d34-acaf-d7f38b092c98@googlegroups.com> (permalink)
Subject	Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--'
From	Alex Vinokur <alex.vinokur@gmail.com>

Show all headers | View raw

On Tuesday, October 2, 2012 7:14:38 PM UTC+2, Tauno Voipio wrote:
> On 2.10.12 5:20 , Alex Vinokur wrote:
> 
> > On Tuesday, October 2, 2012 4:09:38 PM UTC+2, Richard Kettlewell wrote:
> 
> >> Alex Vinokur <alex.vinokur@gmail.com> writes:
> 
> >>
> 
> >>> Could anybody explain why we have 'Permission denied' here?
> 
> >>
> 
> >>>
> 
> >>
> 
> >>> Thanks
> 
> >>
> 
> >>>
> 
> >>
> 
> >>>
> 
> >>
> 
> >>>
> 
> >>
> 
> >>>> uname -a
> 
> >>
> 
> >>> Linux machine1 2.6.32-279.el6.x86_64 #1 SMP Wed Jun 13 18:24:36 EDT 2012 x86_64 x86_64 x86_64 GNU/Linux
> 
> >>
> 
> >>>
> 
> >>
> 
> >>>> id
> 
> >>
> 
> >>> uid=75308(user1) gid=100(users) groups=100(users)
> 
> >>
> 
> >>>
> 
> >>
> 
> >>>> ps -ef | grep 25796
> 
> >>
> 
> >>> root     25796 15752  0 15:11 pts/30   00:00:00 ssh -l root machine2
> 
> >>
> 
> >>> user1    26737 13908  0 15:19 pts/23   00:00:00 grep 25796
> 
> >>
> 
> >>>
> 
> >>
> 
> >>>> ls -ld /proc/25796/maps
> 
> >>
> 
> >>> -r--r--r-- 1 root root 0 Oct  2 15:12 /proc/25796/maps
> 
> >>
> 
> >>>
> 
> >>
> 
> >>>> cat /proc/25796/maps
> 
> >>
> 
> >>> cat: /proc/25796/maps: Permission denied
> 
> >>
> 
> >>
> 
> >>
> 
> >> Because there's an extra check built into the kernel to stop you reading
> 
> >>
> 
> >> that file without a matching UID or the ptrace capability.
> 
> >>
> 
> >>
> 
> >>
> 
> >> --
> 
> >>
> 
> >> http://www.greenend.org.uk/rjk/
> 
> >
> 
> > Thanks,
> 
> >
> 
> > But the file has -r--r--r-- permissions.
> 
> > So, any process with any effective user may read such a file.
> 
> >
> 
> >
> 
> >> ls -ld /proc/25796/maps
> 
> > -r--r--r-- 1 root root 0 Oct  2 15:12 /proc/25796/maps
> 
> 
> 
> 
> 
> The 'files' in /proc are no regular files. They are peepholes into the
> 
> internals of the kernel. The kernel may impose whatever additional
> 
> restrictions it deems fit.
> 
> 
In this case their permissions should be -r--------  or -r--r-----, but not -r--r--r-- (i.e., 0400 or 0440, but not 0444).

Regards,

Alex

Back to comp.os.linux.development.system | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

"Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Alex Vinokur <alex.vinokur@gmail.com> - 2012-10-02 07:05 -0700
  Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Richard Kettlewell <rjk@greenend.org.uk> - 2012-10-02 15:09 +0100
    Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Alex Vinokur <alex.vinokur@gmail.com> - 2012-10-02 07:20 -0700
      Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2012-10-02 20:14 +0300
        Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Alex Vinokur <alex.vinokur@gmail.com> - 2012-10-02 10:46 -0700
          Re: "Permission denied" while reading file /proc/<pid>/maps with   permissions '-r--r--r--' Josef Moellers <josef.moellers@invalid.invalid> - 2012-10-03 12:39 +0200
            Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-10-11 01:53 +0300
            Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-10-11 01:58 +0300
      Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Richard Kettlewell <rjk@greenend.org.uk> - 2012-10-02 20:08 +0100
        Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' pacman@kosh.dhis.org (Alan Curry) - 2012-10-02 21:44 +0000
          Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Alex Vinokur <alex.vinokur@gmail.com> - 2012-10-02 23:16 -0700
          Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Richard Kettlewell <rjk@greenend.org.uk> - 2012-10-03 09:35 +0100
  Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' a.c.kalker@gmail.com - 2013-07-14 06:08 -0700
    Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Jorgen Grahn <grahn+nntp@snipabacken.se> - 2013-07-14 17:08 +0000
    Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' crankypuss <crankypuss@nomail.invalid> - 2013-07-15 02:41 -0600
      Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Jorgen Grahn <grahn+nntp@snipabacken.se> - 2013-07-15 10:06 +0000
    Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Richard Kettlewell <rjk@greenend.org.uk> - 2013-07-15 10:05 +0100
      Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' crankypuss <crankypuss@nomail.invalid> - 2013-07-15 03:51 -0600
        Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Richard Kettlewell <rjk@greenend.org.uk> - 2013-07-15 11:32 +0100
          Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' crankypuss <crankypuss@nomail.invalid> - 2013-07-16 03:50 -0600
            Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Richard Kettlewell <rjk@greenend.org.uk> - 2013-07-16 11:29 +0100
              Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' crankypuss <crankypuss@nomail.invalid> - 2013-07-16 04:53 -0600
                Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Rainer Weikusat <rweikusat@mssgmbh.com> - 2013-07-16 13:06 +0100
                Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' crankypuss <crankypuss@nomail.invalid> - 2013-07-17 01:52 -0600
            Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' Jorgen Grahn <grahn+nntp@snipabacken.se> - 2013-07-16 19:04 +0000
              Re: "Permission denied" while reading file /proc/<pid>/maps with permissions '-r--r--r--' crankypuss <crankypuss@nomail.invalid> - 2013-07-17 02:21 -0600

csiph-web