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Date: Sun, 23 Mar 1997 13:46:19 +0800 (WST)
From: Peter Wemm <peter@spinner.DIALix.COM>
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To: FreeBSD-gnats-submit@freebsd.org
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Subject: kern/3064: nfs server link() handler panics with non-recursive lock reentry
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>Number:         3064
>Category:       kern
>Synopsis:       nfs server link() handler panics with non-recursive lock reentry
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Mar 22 21:50:02 PST 1997
>Last-Modified:
>Originator:     Peter Wemm
>Organization:
Not.
>Release:        FreeBSD 3.0-CURRENT i386
>Environment:

A very -current system, but it's been happening since the Lite2 merge.

FreeBSD spinner.DIALix.COM 3.0-CURRENT FreeBSD 3.0-CURRENT #187: Sun Mar 23 01:43:29 WST 1997     peter@spinner.DIALix.COM:/home/src/sys/compile/SPINNER  i386

>Description:

Any machine can crash a -current system that exports filesystems to it.
The nfs_link() code on the server tries to re-aquire a non-recursive lock
when the destination filename already exists.

>How-To-Repeat:

$ cd /nfs/3_0_current_machine/anywhere_writeable
$ touch xx yy
$ ln -f xx yy

At this point, the 3.0-current machine panics with "locking against myself"
meaning that it's tried to reaquire a lock that is not LK_RECURSIVE.

I found this when sharing a .Xauthaurity file between two machines over
local nfs. xauth(1) triggers the bug, especially when ssh does X11
tunneling/xauth forwarding.

>Fix:
	
Not known.. I don't understand vnode locking under lite2 well enough.
>Audit-Trail:
>Unformatted: