Is it safe to lock the screen with the gnome-screensaver?

Question

USB driver bug exposed as "Linux plug&pwn" or this link

Two choices [GNOME, Fedora 14]:

1 - use the gnome-screensaver
2 - use the "switch user" function [gnome menu -> log out -> switch user]

So the question is: which one is the safer method to lock the screen, if a user leaves the pc?

Is it true, that using the [2] method is safer?

Why do i think this? - The gnome-screensaver is just a "process", it could be killed. But if you use the log out/switch user function, it's "something else". Using the "switch user" function, could there be a problem like with the gnome-screensaver? Could someone "kill a process" and presto...the lock is removed?
Could the GDM [??] "login windows process" [e.g.: a picture of it] get killed and the "lock" gets owned?
Thank you for any opinion!

p.s.: if the [2] method is safer, then how can i put an icon on the GNOME panel, to launch the "switch user" action by 1 click?

Answer 1

The "Switch user" command does only two things:

1. It flips between two X11 servers, yours and the one GDM is running on;
2. It commands the screensaver to lock your session.

In other words, it does not add any more protection.

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However, if you are using a kernel that is vulnerable to a bug in the USB driver, no screen locker in the world can protect against it. Even if you make a process that is absolutely unkillable and bulletproof, one with ability to execute code in kernelspace can bypass any userspace locks.

Therefore, the right solution is to fix the kernel vulnerability.

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Regarding your second link, "GNOME screen lock ineffective in openSUSE Linux", it's from February 2010, and has been fixed in GNOME 2.28.1 as the article itself says.