Bad file access on the rise

[Lennart Poettering]

On Mon, 10.06.13 16:01, Simo Sorce (simo at redhat.com) wrote:

> On Sun, 2013-06-09 at 17:17 +0200, Lennart Poettering wrote:
> > On Fri, 07.06.13 22:33, Richard W.M. Jones (rjones at redhat.com) wrote:
> > 
> > > On Fri, Jun 07, 2013 at 06:55:46PM +0200, Lennart Poettering wrote:
> > > > User "simo" creates /dev/shm/1000/ even though 1000 is the UID of user
> > > > "lennart". Lennart can never start PA again, ever. And can't do anything
> > > > about it, because "simo" is in control, and /dev/shm is sticky.
> > > 
> > > For /run we create /run/user/<uid> in pam_systemd (I think?).
> > > Can we do the same for /dev/shm/<uid>?
> > 
> > There's no benefit in doing that.
> > 
> > /run/user is not world-writable. Hence creating this dir at login time
> > is totally safe, since only trusted code can create dirs in there. This
> > is different for /dev/shm which is world-writable, and where creating
> > dirs at login doesn't solve anything, because any unprivileged user
> > could easily create dirs for all users and then make it impossible to
> > log in for them.
> 
> All this makes me wonder, why are you using /dev/shm at all if it is so
> bad ? There are many other ways to do IPC, so what's keeping you
> on /dev/shm ?

XDG_RUNTIME_DIR is newer than PA. And POSIX shared memory
(i.e. /dev/shm/) s still the best option if you actually want a shared
namespace for the segments...

Lennart

-- 
Lennart Poettering - Red Hat, Inc.