Hello!

I tried the current mainline Linux on Fedora 16 x64_64 and found that I
cannot login in gdm.  I'm using gdm with LXDE.  After a few minutes,
kernel messages appear indicating a hung process gnome-settings-daemon.

Bisection found that the commit to blame is

commit 8280d16172243702ed43432f826ca6130edb4086
Author: Al Viro <viro@zeniv.linux.org.uk>
Date:   Tue Aug 21 12:11:46 2012 -0400

    new helper: replace_fd()

    analog of dup2(), except that it takes struct file * as source.

    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Reverting the part of the patch that changes fs/exec.c is sufficient to
fix the login behavior.

I was able to forward port the change to the current mainline Linux.
The call to replace_fd() was moved to fs/coredump.c, so the patch
changes it.  Also, it copies __clear_close_on_exec() and
__set_open_fd() from fs/file.c

The .config file, the kernel log and the forward ported patch are
attached.

I'll try to figure out why replace_fd() is not good in
umh_pipe_setup(), but I'd like to report the problem as soon as
possible, as it's very visible to the users and I don't want others to
spend hours bisecting it.

-- 
Regards,
Pavel Roskin