Bug#758299: startx: X server fails to start, strace shows permission error

[Aureliano Vismundo <xrs@mail36.net>]

Package: xinit
Version: 1.3.2-1
Severity: important

Dear Maintainer,

I was connecting my monitor with my laptop to do some writing stuff. 
This is normally fine, well it fails sometimes but then I restart 
my computer. This time
it failed again and I thought, good time to update debian. So I did.
libc6-dev, linux-headers, and linux-image were updated. After that
I restarted and when it came to call "startx" the X server did exit
gracefully with no error. And here I am with no GUI.

I first checked /var/log/Xorg.0.log but nothing special, no errors
and no important warnings in my eyes. Then I used strace -ff which 
gave me interesting information about the X server, e.g.:
  * setresuid(-1, 0, -1) = -1  EPERM (Operation not permitted)
  * rename("/var/log/Xorg.0.log", "/var/log/Xorg.0.log.old") = -1 EACCES 
(Permission denied)
  * "Fatal Server error" and "Cannot move old log file /var/log/Xorg.
0.log to /var/log/Xorg.0.log.old"

This seemed to be a simple privileg issue. I tested "sudo startx"
which got X running. Next, I checked if /usr/bin/X and /usr/bin/Xorg had
suid. The first one yes, second one no. I tried chmod u+s /usr/bin/Xorg.
But startx still didn't work without sudo.

I also deleted /var/log/Xorg*. Same result. And put them again in place.

My guess is, that it has something to do with the new kernel version 
and the x server. 
I had no time for further testing.

I would appreciate your help,
aureliano

-- System Information:
Debian Release: 7.6
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages xinit depends on:
ii  coreutils   8.13-3.5
ii  libc6       2.13-38+deb7u3
ii  libx11-6    2:1.5.0-1+deb7u1
ii  x11-common  1:7.7+3~deb7u1
ii  xauth       1:1.0.7-1

Versions of packages xinit recommends:
ii  i3-wm [x-window-manager]     4.2-2
ii  xserver-xorg [xserver]       1:7.7+3~deb7u1
ii  xterm [x-terminal-emulator]  278-4

xinit suggests no packages.

-- no debconf information