Bug#775941: gcab: null pointer dereference

[Jakub Wilk]

Package: gcab
Version: 0.4-2
Usertags: afl

gcab crashes on the attached file:

$ gcab -t crash.cab
Segmentation fault


GDB says it's a null pointer derefence:

Program received signal SIGSEGV, Segmentation fault.
0xf7c760ad in gcab_cabinet_load (self=0x8056420, stream=0x80604d8, 
cancellable=0x8054c10, error=0xffffd5ac) at libgcab/gcab-cabinet.c:388
388             GCabFolder *folder = g_ptr_array_index (folders, cfile.index);
(gdb) print *folders
$1 = {pdata = 0x0, len = 0}


This bug was found using American fuzzy lop:
https://packages.debian.org/experimental/afl



-- System Information:
Debian Release: 8.0
 APT prefers unstable
 APT policy: (990, 'unstable'), (500, 'experimental')
Architecture: i386 (x86_64)
Foreign Architectures: amd64

Kernel: Linux 3.2.0-4-amd64 (SMP w/2 CPU cores)
Locale: LANG=C, LC_CTYPE=pl_PL.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)

Versions of packages gcab depends on:
ii  libc6          2.19-13
ii  libgcab-1.0-0  0.4-2
ii  libglib2.0-0   2.42.1-1

--
Jakub Wilk

Disclaimer: I don't have spare CPU cycles, so I fuzzed only till the first crash (which took a few seconds). It's likely that extensive fuzzing would uncover more interesting crashers. I'd encourage gcab maintainers to perform fuzzing with AFL on their own. :-)

crash.cab
Description: application/cab