Re: capabilities patch (v 0.1)

[daw@cs.berkeley.edu (David Wagner)]

David Madore  wrote:
>I intend to add a couple of capabilities which are normally available
>to all user processes, including capability to exec(), [...]

Once you have a mechanism that lets you prevent the untrusted program
from exec-ing a setuid/setgid program (such as your bounding set idea),
I don't see any added value in preventing the program from calling exec().

"Don't forbid what you can't prevent".  The program can always emulate
the effect of exec() in userspace (for non-setuid/setgid programs) --
doing so is tedious, but nothing prevents a malicious userspace program
from implementing such a thing, I think.

This is only a comment on forbidding exec(), not on anything else in
your proposal.