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

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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 

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"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

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