Re: [gdm-list] [PATCH] fix race condition when setting the model for the face browser

[Ludwig Nussel <ludwig nussel suse de>]

Brian Cameron wrote:
> > - The way pictures are transported into the greeter is really ugly.
> >   IMHO the greeter could just as well open the files itself. There
> >   is no need to let the slave process do it.
> 
> Yes it is ugly.  The problem is that the GUI runs as the gdm user
> and the gdm user does not necessarily have read access to user's
> $HOME directory.  The daemon runs as root and has the ability to
> read image files without these sorts of problems.

If the homes are on nfs root likely gets mapped to nobody and has no
access either. If you want anyone to access stuff in your home you
just have to have o+x (or set an ACL for the gdm user). Apache
doesn't read your ~/public_html if it can't walk through ~ either.
I'm not sure how kdm handles that. IIRC it has even uglier code that
temporarly changes the uid to the target user.

> Probably a better mechanism for passing the images from the daemon
> to the GUI could be devised.  Perhaps the daemon should copy them to
> a location where the GUI can find them (somewhere like /var/tmp/gdm)
> rather than sending them over the sockets connection.
> 
> Note GDM can be configured to use GlobalFaceDir instead of reading
> the image files from the user's $HOME directory, but even in this
> case I think the daemon dumbly sends the images over the wire rather
> than having the GUI just access the images from there directly.

Code for accepting file names instead of the binary image itself is
already there though. That doesn't fix the problem that the protocol
isn't designed for messages originating from the ui though. The
slave requests something and the ui responds, not the other way
around (except for interruptions).

cu
Ludwig

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