Re: [RFC] [PATCH] file posix capabilities

From: Serge E. Hallyn
Date: Tue Aug 15 2006 - 08:18:05 EST

Quoting Serge E. Hallyn (serge@xxxxxxxxxx):
> > Make it an arbitrary length bitfield with a defined byte order (little
> > endian, probably). Bits at offsets greater than the length of the
> > bitfield are defined to be zero. If the kernel encounters a set bit that
> > it doesn't recognizes, fail with EPERM. If userspace attempts to set a
> > bit that the kernel doesn't recognize, fail with EINVAL.
> >
> > It's extensible (as new capability bits are added, the length of the
> > bitfield grows), backward compatible (as long as there are no unknown
> > bits set, it'll still work) and secure (if an unknown bit is set, the
> > kernel fails immediately, so there's no chance of a "secure" app running
> > with less privileges than it expects and opening up a security hole).
> Sounds good.
> The version number will imply the bitfield length, or do we feel warm
> fuzzies if the length is redundantly encoded in the structure?

nm, 'encoded in the structure' clearly is silly.

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