Heap-buffer overread in gsf_mem_dump_full on a fuzzed xls file.

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

Test case: http://jutaky.com/fuzzing/gnumeric_case_29042_24204.xls

==7730== ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60060007f890 at pc 0x7ff2887c3ac7 bp 0x7fff5b0429e0 sp 0x7fff5b0429d8
READ of size 1 at 0x60060007f890 thread T0
    #0 0x7ff2887c3ac6 in gsf_mem_dump_full /libgsf/gsf/gsf-utils.c:254
    #1 0x7ff2887c3ee5 in gsf_mem_dump /libgsf/gsf/gsf-utils.c:284
    #2 0x7ff26768ad2e in excel_parse_formula1 /gnumeric/plugins/excel/ms-formula-read.c:1803 (discriminator 3)
    #3 0x7ff26768b37b in excel_parse_formula /gnumeric/plugins/excel/ms-formula-read.c:1844
    #4 0x7ff2675bf24c in ms_sheet_parse_expr_internal /gnumeric/plugins/excel/ms-excel-read.c:302
    #5 0x7ff267601309 in excel_read_CF /gnumeric/plugins/excel/ms-excel-read.c:5212
    #6 0x7ff2676038d9 in excel_read_CONDFMT /gnumeric/plugins/excel/ms-excel-read.c:5420
    #7 0x7ff26761832e in excel_read_sheet /gnumeric/plugins/excel/ms-excel-read.c:6736
    #8 0x7ff26761b6b0 in excel_read_BOF /gnumeric/plugins/excel/ms-excel-read.c:6994
    #9 0x7ff26761cd5e in excel_read_workbook /gnumeric/plugins/excel/ms-excel-read.c:7084
    #10 0x7ff267592bfc in excel_enc_file_open /gnumeric/plugins/excel/boot.c:193
    #11 0x7ff26759389a in excel_file_open /gnumeric/plugins/excel/boot.c:250
    #12 0x7ff28902400e in go_plugin_loader_module_func_file_open /goffice/goffice/app/go-plugin-loader-module.c:282
    #13 0x7ff28902cf70 in go_plugin_file_opener_open /goffice/goffice/app/go-plugin-service.c:685 (discriminator 1)
    #14 0x7ff2890398bf in go_file_opener_open /goffice/goffice/app/file.c:417
    #15 0x7ff28a18f684 in workbook_view_new_from_input /gnumeric/src/workbook-view.c:1281
    #16 0x7ff28a18fe73 in workbook_view_new_from_uri /gnumeric/src/workbook-view.c:1341
    #17 0x40a6e0 in main /gnumeric/src/main-application.c:322
    #18 0x7ff284917bc4 in __libc_start_main ??:?
    #19 0x403de8 in _start ??:?
0x60060007f890 is located 0 bytes to the right of 32-byte region [0x60060007f870,0x60060007f890)

--
Juha Kylmänen
Research Assistant, OUSPG