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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: comp.os.minix
Subject: Re: Request for help with rmdir bug
Message-ID: <8135@utzoo.UUCP>
Date: Mon, 8-Jun-87 15:13:02 EDT
Article-I.D.: utzoo.8135
Posted: Mon Jun  8 15:13:02 1987
Date-Received: Mon, 8-Jun-87 15:13:02 EDT
References: <1195@botter.cs.vu.nl>
Organization: U of Toronto Zoology
Lines: 16

> The question is: does anyone have an idea how to make rmdir work without
> modifying the kernel.  Unlinking the directory before removing . and ..
> does not sound like a good idea.

This is a known bug in old Unixes.  The simplest approach is to have rmdir
disallow removals of directories with pathnames involving "." or "..".

The fundamental problem is that the removal of the three links is not an
atomic operation.  Even if one fixes rmdir to be proof against tricky
pathnames, more subtle problems can arise because in a multiprogramming
system, other things can be manipulating the directories at the same time.
The only complete fix for race conditions and such is to move the mkdir
and rmdir operations into the kernel.
-- 
"There is only one spacefaring        Henry Spencer @ U of Toronto Zoology
nation on Earth today, comrade."   {allegra,ihnp4,decvax,pyramid}!utzoo!henry