Out-of-bounds read in xlsx-read.c:3876 on a fuzzed xlsx file

Git versions of glib, goffice, gnumeric, libgsf and libxml2.

Test case: http://jutaky.com/fuzzing/gnumeric_case_3283_2648.xlsx

$ ssconvert gnumeric_case_3283_2648.xlsx /tmp/out.gnumeric

==30884==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x7f65a9e62008 bp 0x7ffd0f77fef0 sp 0x7ffd0f77fc00 T0)
    #0 0x7f65a9e62007 in xlsx_comment_start gnumeric/gnumeric/plugins/excel/xlsx-read.c:3876:8
    #1 0x7f65cb92c555 in push_child gnumeric/libgsf/gsf/gsf-libxml.c:658:3
    #2 0x7f65cb9453dd in lookup_child gnumeric/libgsf/gsf/gsf-libxml.c:694:5
    #3 0x7f65cb940400 in gsf_xml_in_start_element gnumeric/libgsf/gsf/gsf-libxml.c:786:7
    #4 0x7f65ca908b60 in xmlParseStartTag__internal_alias gnumeric/libxml2/parser.c:8676:6
    #5 0x7f65ca91471f in xmlParseElement__internal_alias gnumeric/libxml2/parser.c:10080:9
    #6 0x7f65ca912bd3 in xmlParseContent__internal_alias gnumeric/libxml2/parser.c:9990:6
    #7 0x7f65ca917039 in xmlParseElement__internal_alias gnumeric/libxml2/parser.c:10163:5
    #8 0x7f65ca912bd3 in xmlParseContent__internal_alias gnumeric/libxml2/parser.c:9990:6
    #9 0x7f65ca917039 in xmlParseElement__internal_alias gnumeric/libxml2/parser.c:10163:5
    #10 0x7f65ca912bd3 in xmlParseContent__internal_alias gnumeric/libxml2/parser.c:9990:6
    #11 0x7f65ca917039 in xmlParseElement__internal_alias gnumeric/libxml2/parser.c:10163:5
    #12 0x7f65ca912bd3 in xmlParseContent__internal_alias gnumeric/libxml2/parser.c:9990:6
    #13 0x7f65ca917039 in xmlParseElement__internal_alias gnumeric/libxml2/parser.c:10163:5
    #14 0x7f65ca93b684 in xmlParseDocument__internal_alias gnumeric/libxml2/parser.c:10849:2
    #15 0x7f65cb92cc63 in gsf_xml_in_doc_parse gnumeric/libgsf/gsf/gsf-libxml.c:1338:2
    #16 0x7f65a9e3ecd8 in xlsx_parse_stream gnumeric/gnumeric/plugins/excel/xlsx-read.c:358:13
    #17 0x7f65a9e45eba in xlsx_wb_end gnumeric/gnumeric/plugins/excel/xlsx-read.c:4002:4
    #18 0x7f65cb941b81 in gsf_xml_in_end_element gnumeric/libgsf/gsf/gsf-libxml.c:863:3
    #19 0x7f65ca90b856 in xmlParseEndTag1 gnumeric/libxml2/parser.c:8747:9
    #20 0x7f65ca917d3a in xmlParseElement__internal_alias gnumeric/libxml2/parser.c:10191:2
    #21 0x7f65ca93b684 in xmlParseDocument__internal_alias gnumeric/libxml2/parser.c:10849:2
    #22 0x7f65cb92cc63 in gsf_xml_in_doc_parse gnumeric/libgsf/gsf/gsf-libxml.c:1338:2
    #23 0x7f65a9e3ecd8 in xlsx_parse_stream gnumeric/gnumeric/plugins/excel/xlsx-read.c:358:13
    #24 0x7f65a9e3d652 in xlsx_file_open gnumeric/gnumeric/plugins/excel/xlsx-read.c:5153:4
    #25 0x7f65cc500c80 in go_plugin_loader_module_func_file_open gnumeric/goffice/goffice/app/go-plugin-loader-module.c:282:3
    #26 0x7f65cc514804 in go_plugin_file_opener_open gnumeric/goffice/goffice/app/go-plugin-service.c:685:2
    #27 0x7f65cc522018 in go_file_opener_open gnumeric/goffice/goffice/app/file.c:417:2
    #28 0x7f65cdea8f2a in workbook_view_new_from_input gnumeric/gnumeric/src/workbook-view.c:1278:3
    #29 0x7f65cdea9b20 in workbook_view_new_from_uri gnumeric/gnumeric/src/workbook-view.c:1337:9
    #30 0x4e0f21 in convert gnumeric/gnumeric/src/ssconvert.c:715:9
    #31 0x4decce in main gnumeric/gnumeric/src/ssconvert.c:903:9
    #32 0x7f65c693778f in __libc_start_main (/usr/lib/libc.so.6+0x2078f)
    #33 0x437b98 in _start (apps/bin/ssconvert+0x437b98)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV gnumeric/gnumeric/plugins/excel/xlsx-read.c:3876 xlsx_comment_start

--
Juha Kylmänen