Wireshark · Wireshark-bugs: [Wireshark-bugs] [Bug 11518] New: Possible problems with fragment_add and zero-lengths fragment data

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Bug ID	11518
Summary	Possible problems with fragment_add and zero-lengths fragment data lengths
Product	Wireshark
Version	Git
Hardware	All
OS	All
Status	UNCONFIRMED
Severity	Major
Priority	Low
Component	Dissection engine (libwireshark)
Assignee	bugzilla-admin@wireshark.org
Reporter	peter@lekensteyn.nl

Build Information:
TShark (Wireshark) 1.99.10 (v1.99.10rc0-78-g61f07f1 from master)

Copyright 1998-2015 Gerald Combs <gerald@wireshark.org> and contributors.
License GPLv2+: GNU GPL version 2 or later
<http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiled (64-bit) with libpcap, with POSIX capabilities (Linux), with libnl 3,
with libz 1.2.8, with GLib 2.44.1, without SMI, without c-ares, without ADNS,
with Lua 5.2, with GnuTLS 3.4.4, with Gcrypt 1.6.3, with MIT Kerberos, with
GeoIP.

Running on Linux 4.1.6-1-ARCH, with locale en_GB.UTF-8, with libpcap version
1.7.4, with libz 1.2.8, with GnuTLS 3.4.4, with Gcrypt 1.6.3.
Intel(R) Core(TM) i5 CPU       M 560  @ 2.67GHz (with SSE4.2)

Built using gcc 5.2.0.
--
Frame 7488 from bug 10605 triggers addition of a zero-length of a fragment in
the IP dissector (because iph->ip_len - hlen is zero in the IP dissector):

  if (ip_defragment && (iph->ip_off & (IP_MF|IP_OFFSET)) &&
      tvb_bytes_exist(tvb, offset, iph->ip_len - hlen) &&
      ipsum == 0) {
    ipfd_head = fragment_add_check(&ip_reassembly_table, tvb, offset,
                                   pinfo,
                                   iph->ip_p ^ iph->ip_id ^ src32 ^ dst32,
                                   NULL,
                                   (iph->ip_off & IP_OFFSET) * 8,
                                   iph->ip_len - hlen,
                                   iph->ip_off & IP_MF);

    next_tvb = process_reassembled_data(tvb, offset, pinfo, "Reassembled IPv4",
                                        ipfd_head, &ip_frag_items,
                                        &update_col_info, ip_tree);

A backtrace can be found on the end of this description. This report looks like
https://code.wireshark.org/review/9689 and it probably occurs at other places
as well. At a quick glance, I am not sure how this situation should be handled.
What should this API do for zero-length packets? Ignore it, DISSECTOR_ASSERT or
something else? The documentation is not clear on this.


epan/tvbuff.c:783:10: runtime error: null pointer passed as argument 1, which
is declared to never be null
    #0 0x7f87436d4108 in tvb_memcpy epan/tvbuff.c:783
    #1 0x7f87436d432d in tvb_generic_clone_offset_len epan/tvbuff.c:392
    #2 0x7f87436d443e in tvb_clone_offset_len epan/tvbuff.c:411
    #3 0x7f87436ddabb in subset_clone epan/tvbuff_subset.c:94
    #4 0x7f87436d442b in tvb_clone_offset_len epan/tvbuff.c:406
    #5 0x7f87436ddabb in subset_clone epan/tvbuff_subset.c:94
    #6 0x7f87436d442b in tvb_clone_offset_len epan/tvbuff.c:406
    #7 0x7f87436ddabb in subset_clone epan/tvbuff_subset.c:94
    #8 0x7f87436d442b in tvb_clone_offset_len epan/tvbuff.c:406
    #9 0x7f87436ddabb in subset_clone epan/tvbuff_subset.c:94
    #10 0x7f87436d442b in tvb_clone_offset_len epan/tvbuff.c:406
    #11 0x7f87436ddabb in subset_clone epan/tvbuff_subset.c:94
    #12 0x7f87436d442b in tvb_clone_offset_len epan/tvbuff.c:406
    #13 0x7f87436ddabb in subset_clone epan/tvbuff_subset.c:94
    #14 0x7f87436d442b in tvb_clone_offset_len epan/tvbuff.c:406
    #15 0x7f87436a36df in fragment_add_work epan/reassemble.c:1022
    #16 0x7f87436a60dd in fragment_add_check epan/reassemble.c:1457
    #17 0x7f8743de367b in dissect_ip_v4 epan/dissectors/packet-ip.c:2397
    #18 0x7f8743de3dab in dissect_ip epan/dissectors/packet-ip.c:2481
    #19 0x7f874363fc6f in call_dissector_through_handle epan/packet.c:620
    #20 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #21 0x7f87436467af in call_dissector_only epan/packet.c:2570
    #22 0x7f87436467ca in call_dissector_with_data epan/packet.c:2583
    #23 0x7f874364871b in call_dissector epan/packet.c:2600
    #24 0x7f87443d18e4 in dissect_sndcp epan/dissectors/packet-sndcp.c:310
    #25 0x7f874363fc6f in call_dissector_through_handle epan/packet.c:620
    #26 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #27 0x7f87436424de in dissector_try_uint_new epan/packet.c:1163
    #28 0x7f8743642566 in dissector_try_uint epan/packet.c:1189
    #29 0x7f8743c75b4b in dissect_llcgprs epan/dissectors/packet-gprs-llc.c:996
    #30 0x7f874363fc6f in call_dissector_through_handle epan/packet.c:620
    #31 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #32 0x7f87436467af in call_dissector_only epan/packet.c:2570
    #33 0x7f87436467ca in call_dissector_with_data epan/packet.c:2583
    #34 0x7f874364871b in call_dissector epan/packet.c:2600
    #35 0x7f8743927ccb in de_bssgp_llc_pdu epan/dissectors/packet-bssgp.c:943
    #36 0x7f8743c8e8de in elem_telv epan/dissectors/packet-gsm_a_common.c:1399
    #37 0x7f87439318ec in bssgp_ul_unitdata epan/dissectors/packet-bssgp.c:4047
    #38 0x7f8743930fff in dissect_bssgp epan/dissectors/packet-bssgp.c:6444
    #39 0x7f874363fc6f in call_dissector_through_handle epan/packet.c:620
    #40 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #41 0x7f87436467af in call_dissector_only epan/packet.c:2570
    #42 0x7f87436467ca in call_dissector_with_data epan/packet.c:2583
    #43 0x7f874364871b in call_dissector epan/packet.c:2600
    #44 0x7f87440afa67 in decode_pdu_ns_unitdata
epan/dissectors/packet-nsip.c:700
    #45 0x7f87440b04f8 in decode_pdu epan/dissectors/packet-nsip.c:872
    #46 0x7f87440b089a in dissect_nsip epan/dissectors/packet-nsip.c:959
    #47 0x7f874363fc6f in call_dissector_through_handle epan/packet.c:620
    #48 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #49 0x7f87436424de in dissector_try_uint_new epan/packet.c:1163
    #50 0x7f8743642566 in dissector_try_uint epan/packet.c:1189
    #51 0x7f874449bf97 in decode_udp_ports epan/dissectors/packet-udp.c:542
    #52 0x7f87444a079d in dissect epan/dissectors/packet-udp.c:1018
    #53 0x7f87444a0845 in dissect_udp epan/dissectors/packet-udp.c:1025
    #54 0x7f874363fc6f in call_dissector_through_handle epan/packet.c:620
    #55 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #56 0x7f87436424de in dissector_try_uint_new epan/packet.c:1163
    #57 0x7f8743ddfb14 in ip_try_dissect epan/dissectors/packet-ip.c:1972
    #58 0x7f8743de3bc4 in dissect_ip_v4 epan/dissectors/packet-ip.c:2459
    #59 0x7f8743de3dab in dissect_ip epan/dissectors/packet-ip.c:2481
    #60 0x7f874363fc6f in call_dissector_through_handle epan/packet.c:620
    #61 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #62 0x7f87436467af in call_dissector_only epan/packet.c:2570
    #63 0x7f87436467ca in call_dissector_with_data epan/packet.c:2583
    #64 0x7f874364871b in call_dissector epan/packet.c:2600
    #65 0x7f87441ab426 in dissect_raw epan/dissectors/packet-raw.c:149
    #66 0x7f874363fc6f in call_dissector_through_handle epan/packet.c:620
    #67 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #68 0x7f87436424de in dissector_try_uint_new epan/packet.c:1163
    #69 0x7f8743c42044 in dissect_frame epan/dissectors/packet-frame.c:499
    #70 0x7f874363fc2c in call_dissector_through_handle epan/packet.c:618
    #71 0x7f8743640e0c in call_dissector_work epan/packet.c:706
    #72 0x7f87436467af in call_dissector_only epan/packet.c:2570
    #73 0x7f87436467ca in call_dissector_with_data epan/packet.c:2583
    #74 0x7f8743647520 in dissect_record epan/packet.c:498
    #75 0x7f8743617a63 in epan_dissect_run_with_taps epan/epan.c:345
    #76 0x4168a9 in process_packet tshark.c:3719
    #77 0x418484 in load_cap_file tshark.c:3475
    #78 0x41d337 in main tshark.c:2200
    #79 0x7f873a91d60f in __libc_start_main (/usr/lib/libc.so.6+0x2060f)
    #80 0x40a9b8 in _start (/tmp/wsbuild/run/tshark+0x40a9b8)

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