Bug#760768: libfontenc1: outdated zlib1g Depends (causing xfonts-utils mkfontscale Segmentation fault crash)

[Andreas Mohr <andi@lisas.de>]

Package: libfontenc1
Version: 1:1.1.2-1

Hi,

during some updates / reinstalls of xfonts-unifont, I saw

Setting up xfonts-unifont (1:6.3.20140214-1) ...
Segmentation fault

Turned out that the inner command which segfaulted is:
    mkfontscale -b -s -l -e /usr/share/fonts/X11/encodings -e /usr/share/fonts/X11/

which crashes in some libfontenc1 code:

(gdb) run
Starting program: /usr/bin/mkfontscale -e .
warning: Could not load shared library symbols for linux-gate.so.1.
Do you need "set solib-search-path" or "set sysroot"?

Breakpoint 1, FontEncIdentify (fileName=0x8050008 "./.")
    at ../../src/encparse.c:906
906	{
(gdb) n
912	    if((f = FontFileOpen(fileName))==NULL) {
(gdb) 
915	    encoding = parseEncodingFile(f, 1);
(gdb) s
parseEncodingFile (f=f@entry=0x80583c8, headerOnly=headerOnly@entry=1)
    at ../../src/encparse.c:462
462	{
(gdb) n
465	    unsigned short *enc=NULL;
(gdb) 
467	    unsigned i, first = 0xFFFF, last=0, encsize=0, namsize=0;
(gdb) 
480	    line = getnextline(f);
(gdb) s
getnextline (f=f@entry=0x80583c8) at ../../src/encparse.c:196
196	{
(gdb) n
198	    c = FontFileGetc(f);
(gdb) n
196	{
(gdb) n
198	    c = FontFileGetc(f);
(gdb) n

Program received signal SIGSEGV, Segmentation fault.
0xb7fb02b6 in getnextline (f=f@entry=0x80583c8) at ../../src/encparse.c:198
198	    c = FontFileGetc(f);
(gdb) 


Eventually found out that it works on a system with zlib1g 1.2.7.dfsg-13,
yet crashes on a system with 1:1.2.3.4.dfsg-3 .

A simple and successful test is to downgrade a (working) 1.2.7 system
via the 1.2.3.4 package (on my system there fortunately
were no packages installed which had a zlib1g Depends which disallowed that),
and then execute the well-known
    mkfontscale -b -s -l -e /usr/share/fonts/X11/encodings -e /usr/share/fonts/X11/
command again, which now ends up crashing rather than previously working.



Not sure what the policy of specifying newer versions is, though
(theoretically you could simply demand "> 1:1.2.3.4.dfsg-3"
to force an update from the non-compatible older zlib1g version,
or alternatively specifically demand ">= 1.2.7.dfsg-13"
which in this case has been proven to be working.


Finally, it's not quite known
what would constitute a sane libfontenc1 code implementation handling here
anyway - after all we're talking of a somewhat weird gzgetc()
of a gzopen() of filename "./.", i.e. the current-dir entry -
this probably would work for regular files but chooses to crash
for a dir entry (in the older zlib1g version, that is).
So perhaps libfontenc1 should be fixed (instead / as well)
to not do such shenanigans...


ii  libfontenc1:i386                     1:1.1.2-1                         i386         X11 font encoding library
ii  xfonts-utils                         1:7.7+2                           i386         X Window System font utility programs
ii  zlib1g                               1:1.2.3.4.dfsg-3                  i386         compression library - runtime


Thanks,

Andreas Mohr

-- 
GNU/Linux. It's not the software that's free, it's you.