nion's blog

Another nice piece of code made by ESR you know, the guy who writes books about "The art of UNIX programming" for example

From sink.c:


This code will segfault if the fopen call in line 4 fails, sinkfp will become NULL then which leads
to a segfault when writing more than once into it with fprintf/fputs.

What I find funny now is the check in line 17 to test the error indicator for the stream pointed to by sinkfp AFTER actually writing into it.
But what is even more funny is that also the check would segfault in this case since ferror will if it gets a NULL pointer.

Today I wanted to learn for my examns and thought I'd make a quick dist-upgrade before, looked at the packages, found nothing important to make a backup and DANG

All installations with debconf usage didn't succeed like here for example:

dpkg: error processing samba-common (--configure):
subprocess post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of smbclient:
smbclient depends on samba-common (= 3.0.24-6); however:
Package samba-common is not configured yet.
dpkg: error processing smbclient (--configure):
dependency problems - leaving unconfigured

I straced, asked in #debian-devel, read source code and really didn't find the problem.
Thanks Mika for noticing the same problem before I did and the fix was sooo easy.
ln -sf /bin/bash /bin/sh

Never ever link /bin/sh to zsh on Debian