Date: Thu, 19 Apr 2001 11:19:08 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: Terry Lambert <tlambert@primenet.com> Cc: Matt Dillon <dillon@earth.backplane.com>, arch@FreeBSD.ORG Subject: Re: Found BAD BUG: squashed Message-ID: <Pine.BSF.4.21.0104191046120.5481-100000@besplex.bde.org> In-Reply-To: <200104182323.QAA22635@usr07.primenet.com>
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On Wed, 18 Apr 2001, Terry Lambert wrote:
> > :The cr_ref is an unsigned short, and ...
This was fixed in -current in:
RCS file: /home/ncvs/src/sys/sys/ucred.h,v
Working file: ucred.h
head: 1.22
...
----------------------------
revision 1.18
date: 2000/11/27 00:09:16; author: alfred; state: Exp; lines: +11 -3
ucred system overhaul:
...
4) expand the size of the refcount from a u_short to an u_int, by using
shorts we might have an overflow.
Glanced at by: jake
----------------------------
> >
> > Ahhh.. Excellent find Terry!
> >
> > Why do you want to cycle a new credential when the unsigned short
> > ref count reaches 65535 (what you call the right fix) verses simply
> > changing the ref count to an unsigned long (what you call the quick
> > and dirty fix)? That seems kinda reversed to me.
> Because my use is not the common use, and it bloats the cred
> structure to a non-4-byte boundary, which I thought might end
> up being problematic for some people.
Bloatage of struct ucred occurred in 4.4BSD when uid_t's and gid_t's
were changed from 16 bits to 32 bits. "u_short cr_ref" is followed
by "uid_t cr_uid", so there are normally 2 bytes wasted after "cr_ref".
These bytes can used for larger reference counts without changing the
size of the struct, but not without breaking binary compatibility.
Fortunately, "cr_ref" is invalid in userland.
Bruce
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