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NSE/Nsock segfault, script timeouts, NSE runlevel, etc
From: Brandon Enright <bmenrigh () ucsd edu>
Date: Sat, 2 May 2009 04:56:05 +0000

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I have been running into a segfault in NSE/Nsock with the latest SVN
revision.  Patrick *may* already be aware of this and it *may* relate
to this comment:

"This is a symptom of the failing nsock library binding which has
plagued NSE with bugs for a while now. That it happened in
nse-lua-merge is merely happenstance. In the future I hope to clean it
up like I did with the nmap library."

Which Patrick said in:
http://seclists.org/nmap-dev/2009/q1/0798.html


Just in case the segfault isn't related, here is a tidbit more
information.

The final output before the crash was:

...
NSE Timing: About 95.83% done; ETC: 03:54 (0:01:10 remaining)
NSE Timing: About 95.83% done; ETC: 03:54 (0:01:12 remaining)
NSE Timing: About 95.83% done; ETC: 03:55 (0:01:13 remaining)
NSE Timing: About 95.83% done; ETC: 03:55 (0:01:14 remaining)
NSE Timing: About 95.83% done; ETC: 03:56 (0:01:16 remaining)
NSE: smb-brute target timed out
Completed NSE at 03:55, 1756.38s elapsed
NSE: Starting runlevel 2 scan
Initiating NSE at 03:55
NSE: NSE Script Threads (2) running:
NSE: Starting smb-check-vulns against x.y.10.148.
NSE: Starting p2p-conficker against x.y.10.148.
NSE: Conficker: Generating ports based on ip (0x940aXXYY) and seed (2051)
NSE: smb-check-vulns target timed out
NSE: p2p-conficker target timed out
Completed NSE at 03:55, 0.21s elapsed

A backtrace of the segfault is:

(gdb) bt
#0  0x00007f2041642e39 in lua_pushnil () from /usr/lib/liblua.so.5
#1  0x000000000046b645 in l_nsock_checkstatus (L=0x7823df0, 
    nse=<value optimized out>) at nse_nsock.cc:443
#2  0x000000000046b6bc in l_nsock_send_handler (nsp=<value optimized out>, 
    nse=0x66ac660, yield=0x67c0cf0) at nse_nsock.cc:571
#3  0x000000000047bcd0 in msevent_dispatch_and_delete (nsp=0x665e260, 
    nse=0x66ac660, notify=<value optimized out>) at nsock_event.c:297
#4  0x000000000047bdfb in msevent_cancel (nsp=0x665e260, nse=0x66ac660, 
    event_list=0x665e5d0, elem=0x665f3c8, notify=1) at nsock_event.c:271
#5  0x000000000047a850 in nsi_delete (nsockiod=0x78319b0, pending_response=1)
    at nsock_iod.c:181
#6  0x000000000046c824 in l_nsock_close (L=0x6651620) at nse_nsock.cc:794
#7  0x000000000046c8da in l_nsock_gc (L=0x6651620) at nse_nsock.cc:761
#8  0x00007f204164812b in ?? () from /usr/lib/liblua.so.5
#9  0x00007f2041648528 in ?? () from /usr/lib/liblua.so.5
#10 0x00007f2041649daf in ?? () from /usr/lib/liblua.so.5
#11 0x00007f2041649e68 in ?? () from /usr/lib/liblua.so.5
#12 0x00007f204164a2f0 in ?? () from /usr/lib/liblua.so.5
#13 0x00007f20416434f5 in lua_gc () from /usr/lib/liblua.so.5
#14 0x00007f20416564a8 in ?? () from /usr/lib/liblua.so.5
#15 0x00007f204164812b in ?? () from /usr/lib/liblua.so.5
#16 0x00007f2041652e31 in ?? () from /usr/lib/liblua.so.5
#17 0x00007f2041648585 in ?? () from /usr/lib/liblua.so.5
#18 0x00007f2041647d27 in ?? () from /usr/lib/liblua.so.5
#19 0x00007f2041647da5 in ?? () from /usr/lib/liblua.so.5
#20 0x00007f20416436b4 in lua_pcall () from /usr/lib/liblua.so.5
#21 0x0000000000469b39 in run_main (L=0x6651620) at nse_main.cc:457
#22 0x00007f204164812b in ?? () from /usr/lib/liblua.so.5
#23 0x00007f2041648528 in ?? () from /usr/lib/liblua.so.5
#24 0x00007f2041647d27 in ?? () from /usr/lib/liblua.so.5
#25 0x00007f2041647da5 in ?? () from /usr/lib/liblua.so.5
#26 0x00007f2041643657 in lua_cpcall () from /usr/lib/liblua.so.5
#27 0x00000000004699c5 in script_scan (targets= () 0x7fff4a4ad5d0)
    at nse_main.cc:499
#28 0x000000000041cfa6 in nmap_main (argc=35, argv=0x7fff4a4b0868)
    at nmap.cc:1811
#29 0x0000000000418735 in main (argc=35, argv=0x7fff4a4b0868) at main.cc:215


One of the things that jumps out at me as broken is that when a host
has timed out, higher run levels of NSE probably shouldn't be run.
There is no time to run the scripts so they appear to be created and
then destroyed.  I suppose it may be too much work to check to see if
all of the hosts in a hostgroup have timed out or not before running a
higher run level though...  Perhaps script shouldn't be started on
hosts that have already timed out rather than completely skipping the
run level.

Brandon

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