Messages in this thread |  | | From | "H. Peter Anvin" <> | Subject | Re: [RFC] Groups beyond 32 | Date | 17 Jul 2002 16:36:35 -0700 |
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Followup to: <1026936556.25347.48.camel@UberGeek> By author: Austin Gonyou <austin@digitalroadkill.net> In newsgroup: linux.dev.kernel > > The problem now is more one of maintenance. Most distributions do not > support groups > 32 AFAIK. So, it's lead me to ask the following > questions: > > 1. Why, in general, is the limit so low? > For specific application, mainly auditing and such, this would be > advantageous I think. >
Mostly to cap the amount of storage to maintain in kernel space, and for historical reasons.
> 2. What is required to limit the dependence on groups to just GLIBC or > just the kernel? Is that even possible?
The main problem is programs who do things like:
gid_t mygroups[NGROUPS];
Other than that, it should all be in kernel space. According to POSIX, the NGROUPS above really should be sysconf(_SC_NGROUPS_MAX) -- NGROUPS_MAX is defined as a *guaranteed minimum* of sysconf(_SC_NGROUPS_MAX). Obviously there needs to be a kernel -> libc interface for the sysconf.
FWIW, POSIX specifies:
Application writers should note that {NGROUPS_MAX} is not necessarily a constant on all implementations.
(glibc has #define NGROUPS NGROUPS_MAX).
> 3. Is there any true advantage to supporting more than 32 groups, or > creating "meta-groups" to get around the problem?
There probably is.
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