linux-kernel - Re: ls -l /proc/1/exe -> Permission denied

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Message-ID: <CAFLxGvyAzUwMqi5vAGzoUoP6J4m+6FGC-J4=zKG2ZGguTgO8cg@mail.gmail.com>
Date:	Sun, 20 Jul 2014 13:06:30 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Andreas Schwab <schwab@...ux-m68k.org>
Cc:	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: ls -l /proc/1/exe -> Permission denied

On Sun, Jul 20, 2014 at 12:55 PM, Andreas Schwab <schwab@...ux-m68k.org> wrote:
> Joakim Tjernlund <joakim.tjernlund@...nsmode.se> writes:
>
>> Andreas Schwab <schwab@...ux-m68k.org> wrote on 2014/07/19 22:21:59:
>>>
>>> Joakim Tjernlund <joakim.tjernlund@...nsmode.se> writes:
>>>
>>> > Trying to real /proc/<pid>/exe I noticed I could not read links not
>>> > belonging to my user such as:
>>> > jocke >  ls -l /proc/1/exe
>>> >              ls: cannot read symbolic link /proc/1/exe: Permission
>> denied
>>> >
>>> > Is this expected?
>>>
>>> Yes.  This information is considered private.
>>
>> I don't understand why though.
>
> It would allow bypassing access restrictions.

Do you have an example?
I'm asking because an attacker could make any symlink as he wants to.
A ln -s /etc/shadow lala still does not give me access to shadow...

-- 
Thanks,
//richard
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