kern/108968: Double mount then umount and ls resuits in panic.

[Dmitriy]

>Number:         108968
>Category:       kern
>Synopsis:       Double mount then umount and ls resuits in panic.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Feb 09 11:40:16 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Dmitriy
>Release:        6.2-RELEASE
>Organization:
>Environment:
FreeBSD gate.smeu.ru 6.2-RELEASE FreeBSD 6.2-RELEASE #0: Mon Jan 22 09:54:54 NOVT 2007   root at gate.smeu.ru:/usr/src/sys/i386/compile/GATE  i386
>Description:
If you mount CD with "mount /cdrom", then mount it again: "mount /cdrom" and then "umount /cdrom", "cd /cdrom" and "ls", you can see this:

Fatal trap 12: page fault while in kernel mode
fault virtual address	= 0x0
fault code		= supervisor read, page not present
instruction pointer	= 0x20:0xc047d670
stack pointer		= 0x28:0xcb3fbaac
frame pointer		= 0x28:0xcb3fbac0
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		= 819 (ls)
trap number		= 12
panic: page fault
Uptime: 5m12s
Cannot dump. No dump device defined/
Automatic reboot in 15 seconds - press a key on the console to abort

How can you double mount? May be you do something long time after first mount, of may be amnesiac?

You can do this on GENERIC kernel after install without changing anything.
>How-To-Repeat:
Insert CD in CDROM, mount with

mount /cdrom
mount /cdrom
umount /cdrom
cd /cdrom
ls

>Fix:
Newer do double mount and check before mounting.
>Release-Note:
>Audit-Trail:
>Unformatted: