Re: VT_PROCESS, VT_LOCKSWITCH capabilities

[Andrew Morton]

On Wed, 01 Aug 2007 00:22:38 +0200 Frank Benkstein <frank-lkml@xxxxxxxxxxxxx> 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?
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