Re: Breakage from patch: Only root should be able to set the N_MOUSE line discipline.

[Vojtech Pavlik]

On Sat, Feb 26, 2005 at 11:20:44AM +0000, Alan Cox wrote:

> On Gwe, 2005-01-28 at 16:12, Linux Kernel Mailing List wrote:
> > ChangeSet 1.1977.1.2, 2005/01/28 17:12:20+01:00, vojtech@xxxxxxx
> > 
> > 	input: Only root should be able to set the N_MOUSE line discipline.
> > 	
> 
> I finally had a chance to trace down why my mouse code for a little gui
> library started working differently and causing problems. This broken
> change breaks apps that use framebuffer in unpriviledged process form
> and want to use the mouse support in kernel and forces them to become
> setuid root or to revert to 2.4 style user space mouse drivers. If this
> functonality is root only kernel space it might as well be entirely
> deleted IMHO.
> 
> I can see no reason for this change - the ldisc is supposed to be
> configurable by non root users. It is reset on close/hangup in Linux so
> a user cannot jam a port up.
> 
> Can someone please justify this change. If not can it be reverted
 
A nonprivileged user could inject mouse movement and/or keystrokes
(using the sunkbd driver) into the input subsystem, taking over the
console/X, where another user is logged in.

Simply using a slightly modified inputattach on a PTY will do the trick.

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR
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