Mailinglist Archive: opensuse (3574 mails)

[Randall R Schulz <rschulz@xxxxxxxxx>]

On Tuesday 26 February 2008 14:54, Markus Moeller wrote:
> When I su from root to another id I can not anymore list links in
> /proc/'pid'/  of  the original process. This creates a problem when
> for example running perl as root and switching id (using $>) after
> which in some circumstances perl tries to start /proc/self/exe which
> is a link to /usr/bin/perl and fails.
>
> Is this a known bug ?

It's a known behavior, but by no means a bug!

The only way you're going to make this work is by acquiring access 
(opening a file, e.g.) and by then passing that descriptor across the 
ID change back to the restricted UID.

This is possible when writing in C (and many other languages, including 
scripting languages). Doing it from the shell is at best a trickier 
proposition. In particular, while the shell allows much more than the 
usual ">", "<", "|" operators for, I see no indication (in the man or 
info page) that su will participate in such machinations. It may simply 
allow all non-standard descriptors (those other than 0, 1 and 2) to 
persist after the UID change and the new process is executed, it may, 
as a security measure, close all but those descriptors.

You'll have to experiment.


> Thank you
> Markus


Randall Schulz
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