A union mount of a directory onto the same directory causes havoc

[ghost]

Metadata

• Number: 3645
• Originator: Rick Byers <rickb@iaw.on.ca>
• Arrived: Sun May 18 13:05:00 +0000 1997
• Last modified: Mon Jun 07 06:42:23 +0000 1999
• Environment: System: NetBSD rickb.iaw.on.ca 1.2E NetBSD 1.2E (RICKB) small bug in libedit might cause abnormal program termination #3: Sat May 10 20:04:10 EST 1997 root@rickb.iaw.on.ca:/usr/src/sys/arch/i386/compile/RICKB i386

Description

    A union mount from one directory onto the same directory causes the system to pretty much
    lock up.  For A while, I can ps etc, but any disk activity causes it to look up.  The mount
    process (or any other locked process) cannot be killed.  Generally the entire system
    completely locks up pretty quickly.  No special priveledges are required - any directory
    that the user owns can be used.

How to repeat

    mount_union somedir somedir

Fix

    No sure.  Definantly a kernel problem.  I've temporarily disabled the mount_union
    command, but that doesn't stop users from compiling their own program that attempts a 
    union mount.

Audit trail

State-Changed-From-To: open->feedback 
State-Changed-By: hwr 
State-Changed-When: Sat May 8 02:42:23 PDT 1999 
State-Changed-Why:  
Could you try, is this still happens with actual code? It might be that 
this went away with Lite2 merger. (yes, I know that your PR is 2 years old *sigh*) 

From: Rick Byers <rickb@iaw.on.ca>
To: gnats-bugs@netbsd.org
Cc:  Subject: kern/3645
Date: Sun, 23 May 1999 17:22:15 -0400

 The mount_union binary will no longer do this, but the kernel will.  A
 modified binary can still easily crash the system when the UNIONFS is in
 the kernel.
State-Changed-From-To: feedback->open 
State-Changed-By: hwr 
State-Changed-When: Sun Jun 6 23:41:42 PDT 1999 
State-Changed-Why:  
This is still a problem.