Date: Mon, 26 Jan 2015 13:20:28 -0800 From: Devin Teske <dteske@FreeBSD.org> To: Bruce Evans <brde@optusnet.com.au> Cc: Baptiste Daroussin <bapt@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, Slawa Olhovchenkov <slw@zxy.spb.ru>, svn-src-head@freebsd.org, Devin Teske <dteske@FreeBSD.org> Subject: Re: svn commit: r277652 - in head/usr.sbin/pw: . tests Message-ID: <5D58B34B-8647-4B69-8D90-E7D37C98D4AD@FreeBSD.org> In-Reply-To: <20150126014336.P2572@besplex.bde.org> References: <201501241913.t0OJD4xT039188@svn.freebsd.org> <20150125155254.V1007@besplex.bde.org> <20150125142148.GA76051@zxy.spb.ru> <20150126014336.P2572@besplex.bde.org>
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> On Jan 25, 2015, at 7:31 AM, Bruce Evans <brde@optusnet.com.au> wrote: > > On Sun, 25 Jan 2015, Slawa Olhovchenkov wrote: > >> On Sun, Jan 25, 2015 at 04:56:24PM +1100, Bruce Evans wrote: >> >>> Negative ids have historical abuses in places like mountd. Which paves the way for the “accepted practice” argument and backed up by “in-the-field usage” statement(s). >>> mountd still >>> hard-codes -2 and -2 for the default uid and gid of an unprivileged user. >>> It at least casts these values to uid_t and gid_t before using them. >>> This gives the ids the non-random values of UINT32_MAX-1 if uid_t and >>> gid_t are uint32_t. (If uid_t and gid_t were signed, then it would >>> leave the values as negative, so invalid.) These magic values may work >>> better than when ids were 16 bits, since there is less risk of them >>> conflicting with a normal id. However, the non-conflict is probably >>> a bug. FreeBSD uses the magic ids of 65534 for user nobody: group >>> nobody. These would have been (id_t)-2 with 16-bit ids. They no >>> longer match, so ls displays (id_t)-2 numerically. FreeBSD also has >>> a group nogroup = 65553 that doesn't match the nfs usage. However2, >>> in FreeBSD-1 wher ids were 16-bits, nobody was 32767 and nogroup was >>> 32766. so they didn't match nfs for other reasons. The 2 non-groups >>> now seem to be just a bug -- FreeBSD-1 didn't have group nobody. >>> 4.4BSD-Lite2 has the same values as FreeBSD-1. >> >> This is not full true for ZFS case. >> On ZFS nobody is 2^32-2. > > File systems don't get to decide this. +1 (and thanks for the historical account, bruce — sincerely) However, I still want to make the argument that: a. Because we’ve supported mapping negative inputs to unsigned values in pw *for over a decade*, that… b. We should either revert or make a relnotes submission to note that we’re changing the long-standing accepted practice. Changing the accepted practice broke code internally, it would have likely broken some external code as well — and people deserve to know about said change else we should continue to support accepted practice that is decade(s) old. — Devin
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