On Wed, 01 Aug 2007 00:22:38 +0200 Frank Benkstein [off-list ref] wrote:

I wonder why there are different permissions needed for VT_PROCESS
(access to the current virtual console) and VT_LOCKSWITCH
(CAP_SYS_TTY_CONFIG).

The first one lets the calling process decide if console switching is
allowed, the second one simply disables it.  If a program wants to
forbid console switching the only technical difference I can see is that
switching is automatically reenabled when the program exits when using
VT_PROCESS.  When using VT_LOCKSWITCH it must be manually reenabled.
When the program uses the first method and disables terminal signals and
SysRQ is disabled, too, I see no practical difference between the two.

It'd take some kernel archaeology to work out how things got the way they
are.

Perhaps the issue with VT_LOCKSWITCH is that its effects will persist after
the user has logged out?  So user A is effectively altering user B's
console, hence suitable capabilities are needed?

Is the current code actually causing any observable problem?