linux-kernel - [BUMP] [BUG] rename() from outside of the target dir breaks /proc exe symlink.

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Message-ID: <54D8F9F1.4000300@gmail.com>
Date:	Mon, 09 Feb 2015 19:18:25 +0100
From:	Piotr Karbowski <jabberuser@...il.com>
To:	Piotr Karbowski <piotr.karbowski@...il.com>,
	Al Viro <viro@...IV.linux.org.uk>
CC:	linux-kernel@...r.kernel.org
Subject: [BUMP] [BUG] rename() from outside of the target dir breaks /proc
 exe symlink.

On 01/16/2015 07:25 PM, Piotr Karbowski wrote:
> On 12/30/2014 11:40 PM, Piotr Karbowski wrote:
>> Hi Al,
>>
>> On 12/27/2014 07:14 PM, Al Viro wrote:
>>> That's because it never _had_ worked.  Note that opening the damn thing
>>> will give the right file - it does not work by traversing the result of
>>> readlink(2).  readlink(2) output on those is not promised to be useful
>>> in all cases; often enough it is, but it won't work on cross-directory
>>> renames, it can't be used to tell a filename that really ends with "
>>> (deleted)"
>>> from a removed file, etc.  Moreover, it only very recently became
>>> usable for
>>> victim names with the last component longer than 40 characters if you
>>> did an
>>> overwriting rename.
>>>
>>> What are you trying to use it for?
>>
>> I am using it to track the origin of running processes. I am working
>> with continuous integration of a Linux embedded software. The tests goes
>> in Linux containers, multiple instances of binary with the same name in
>> a single container/namespace, all with cwd symlink pointing to / which
>> looks from outside virtually the same, the binaries are modified at
>> runtime by coping, modifing and replacing for another execution of the
>> same binary (using patchelf to add additional NEEDED to header or change
>> rpath or dynamic loader and such).
>>
>> In my very usecase, the exe symlink is essential.
>
> *Friendly bump*
>
> Can anything be done about it or is there any other mechanism that I
> could use to get origin of the running binary?

*Even friendlier bump*

-- Piotr.

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