kern/49184: udf_symlink_long test case panics rump kernel

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         49184
>Category:       kern
>Synopsis:       udf_symlink_long test case panics rump kernel
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Sep 08 14:05:00 +0000 2014
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2014.09.07.09.10.09
>Organization:

>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

I recently added a new test case "symlink_long" to the t_vnops test
program.  This test case creates symlinks with long target names, for a
number of different values of "long", and expects the operation to
either succeed or return ENAMETOOLONG.  It passes for all file systems
except UDF, where it panics the rump kernel:

  panic: kernel diagnostic assertion "old_size > new_size" failed: file 
"/tmp/bracket/build/2014.09.07.09.10.09-i386/src/sys/rump/fs/lib/libudf/../../../../fs/udf/udf_allocation.c",
 line 2957 

Backtrace:

  #5  0xbb886d21 in rumpns_vpanic () from /usr/lib/librump.so.0
  #6  0xbb86a150 in rumpns_kern_assert () from /usr/lib/librump.so.0
  #7  0xbbaccf56 in rumpns_udf_shrink_node () from /usr/lib/librumpfs_udf.so.0
  #8  0xbbac1328 in rumpns_udf_symlink () from /usr/lib/librumpfs_udf.so.0
  #9  0xbb87a1f9 in rumpns_VOP_SYMLINK () from /usr/lib/librump.so.0
  #10 0xbb94d457 in ?? () from /usr/lib/librumpvfs.so.0
  #11 0xbb8c086d in rump_syscall () from /usr/lib/librump.so.0
  #12 0xbb8b4d55 in rump___sysimpl_symlink () from /usr/lib/librump.so.0
  #13 0x0805c644 in symlink_len.constprop ()
  #14 0x0805c7a5 in symlink_long.constprop ()
  #15 0x0806a197 in atfu_udf_symlink_long_body ()
  #16 0xbb674c97 in atf_tc_run () from /usr/lib/libatf-c.so.0
  #17 0xbb671bef in atf_tp_run () from /usr/lib/libatf-c.so.0
  #18 0xbb6716a9 in atf_tp_main () from /usr/lib/libatf-c.so.0
  #19 0x080822fc in main ()

>How-To-Repeat:

cd /usr/tests/fs/vfs
atf-run t_vnops | atf-report

>Fix: