[Zenmap-Patch] MemoryError

[Jay Bosamiya <jaybosamiya () gmail com>]

Hi All!

We get many reports on the mailing list about Zenmap crashing with a
MemoryError. Until we fix the underlying issue, we want to catch this
bug and provide the user a more useful error message so that we get less
of the out-of-memory "crash reports".

If you want to see the bug for yourself:

  * Obviously, if you have low RAM, then you just run Zenmap :P
  * Running Zenmap on a system with lesser memory (or in a VM) is an
    option; however this is cumbersome.
  * Use scans that generate *HUGE* output. This usually takes too long
    if you have enough RAM on your system.
  * The best way I could see is to do the following:
     1. Run |"softlimit -a 1000000000 python zenmap"| to limit the
        memory that Zenmap can use (you may have to tweak the number
        here; this value works well enough for me)
     2. Use |"nmap 127.0.0.1/24 --packet-trace -p- -r|" as the Nmap
        Command in the GUI. This generates extremely large output.
     3. Run the scan and wait for a while
     4. BOOM!
  * Using "nmap 127.0.0.1/24 --packet-trace -p- -r" may be too slow to
    actually wait for scan to complete, so you can use "nmap
    --packet-trace -r --top-ports 1500 127.0.0.1/24" instead.

Fix: The MemoryError is not localized to just the output window and
multiple |try-except| wraps are needed. Each wrap caused one bug to
disappear but allowed me to see the next.
Finally, I was able to identify few key places where the try-except
wraps are enough to catch the MemoryError. Attached is the patch for the
same.

Testing: I have tested each option multiple times and things seem to
work as expected, with every MemoryError being caught. Some (very) rare
crashes do occur, but that is because of the extremely restrictive
environment that I am testing in, and they seem to disappear the moment
I (even marginally) increase the memory I allow Zenmap to use.

Comments are welcome, as always.

Cheers,
Jay

Attachment: catchingMemoryError.patch
Description:

_______________________________________________
Sent through the dev mailing list
http://nmap.org/mailman/listinfo/dev
Archived at http://seclists.org/nmap-dev/