Hi,

Description: lightdm-1.6.2 cannot log in users if their Xauthority file is corrupt.

Steps to reproduce:
- log out
- intentionally truncate your .Xauthority file at a random place.
- try to log in again with lightdm

This upstream fix is critical and caused my machines to prevent me from logging in four times this week (something corrupted my .Xauthority files maybe, but the punishment of not being able to log in anymore is a bit harsh).

This is covered by the critical patch there:

http://bazaar.launchpad.net/~lightdm-team/lightdm/trunk/revision/1803

It's not pushed to the 1.6 branch yet. Assuming you want to stick to the stable branch, you have to apply this patch.

logs in lightdm.log typically show this.

[+151.25s] DEBUG: Session 764 running command /etc/lightdm/Xsession gnome-sessio
n
[+151.54s] DEBUG: Registering session with bus path /org/freedesktop/DisplayMana
ger/Session0
[+151.54s] DEBUG: Session 764 exited with return value 1
[+151.54s] DEBUG: User session quit
[+151.54s] DEBUG: Stopping display

An strace of the lightdm process shows more:

21:48:35.028167 open("/home/thome/.Xauthority", O_RDONLY) = 8
21:48:35.028211 fstat(8, {st_mode=S_IFREG|0600, st_size=363, ...}) = 0
21:48:35.028242 read(8, "\1\0\0\6cochon\0\00216\0\22MIT-MAGIC-COOKIE-1\0\20\222\233\376\354\240glg\36\20\274\30\305\37:$\1\0\0\6cochon\0\00214\0\22MIT-MAGIC-COOKIE-1\0\20p\301wy>G\327\275_\226\236m\375%\373\302\1\0\0\6cochon\0\00213\0\22MIT-MAGIC-COOKIE-1\0\20\344\243\t\305uKW\215\313J\254i\302\252\341P\1\0\0\6cochon\0\00212\0\22MIT-MAGIC-COOKIE-1\0\20\315\367G\372\211 \354\r\334\205\34\340-A\30\261\1\0\0\6cochon\0\00211\0\22MIT-MAGIC-COOKIE-1\0\20G\2265\331\224\345\225\267\254\5\302"..., 363) = 363
21:48:35.028275 close(8) = 0
21:48:35.028331 open("/home/thome/.Xauthority", O_WRONLY|O_CREAT, 0600) = 8
21:48:35.028357 close(8) = 0
21:48:35.028655 tgkill(1367, 1368, SIGRT_1) = 0
21:48:35.028729 futex(0x7fff7460bde0, FUTEX_WAIT_PRIVATE, 1, NULL) = 0
21:48:35.028819 setresuid(0, 0, 4294967295) = 0
21:48:35.028854 tgkill(1367, 1368, SIGRT_1) = 0
21:48:35.028968 setresgid(0, 0, 4294967295) = 0
21:48:35.028995 write(2, "Error writing X authority: Failed to write X authority /home/thome/.Xauthority: Success\n", 88) = 88
21:48:35.029162 exit_group(1) = ?
21:48:35.029560 +++ exited with 1 +++

Also reporting upstream.

Best,

E.