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Date: Thu, 21 May 1998 10:42:45 +0400 (MSD)
From: Alex Povolotsky <tarkhil@asteroid.svib.ru>
Reply-To: tarkhil@asteroid.svib.ru
To: FreeBSD-gnats-submit@freebsd.org
Subject: mount_msdos+mount_null+mc=panic
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>Number:         6706
>Category:       kern
>Synopsis:       mount_msdos+mount_null+mc=panic
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed May 20 23:40:02 PDT 1998
>Closed-Date:    Mon Feb 21 11:33:44 PST 2000
>Last-Modified:  Mon Feb 21 11:35:34 PST 2000
>Originator:     
>Release:        
>Organization:
>Environment:
>Description:
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: gnats-admin->freebsd-bugs 
Responsible-Changed-By: steve 
Responsible-Changed-When: Sat May 23 20:04:23 PDT 1998 
Responsible-Changed-Why:  
Misfiled PR. 
State-Changed-From-To: open->closed 
State-Changed-By: billf 
State-Changed-When: Mon Feb 21 11:33:44 PST 2000 
State-Changed-Why:  
nullfs is known to be buggy, evil, and unstable. Stacking layers need to be 
working for nullfs to work well. When stacking layers are in place and nullfs 
is fixed, I'm sure this will all fall into place. 

Trying this on a more recent version of FreeBSD may even give you reasonable 
success. 
>Unformatted:
FreeBSD (AFAIK from somewhere about 2.2.2 and on)
Midnight Commander (4.XX, maybe older)
Description: 
Attempt to view (using F3 key in MC) any file on mount_null'ed msdos
partition cause kernel to panic

Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0xc
fault code              = supervisor read, page not present
instruction pointer     = 0x8:0xf013c1ea
stack pointer           = 0x10:0xf417ddb8
frame pointer           = 0x10:0xf417ddb8
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 3431 (midc)
interrupt mask          = 
trap number             = 12
panic: page fault

How-To-Repeat: 
mount (using mount -t msdos) any MS-DOS disk
remount (using mount_null) any directory on that disk anywhere
start midnight commander
attempt to view (using F3) any file on mount_null'ed directory
