[committed v3] nisplus: Correct pwent parsing issue and resulting build error [BZ #23266]

["Maciej W. Rozycki" <macro at mips dot com>]

Copy and null-terminate NIS+ password file UID and GID entries whose
length is non-zero and are not terminated, in addition to empty ones,
fixing a bug and a compilation issue causing an error with GCC 8:

nss_nisplus/nisplus-parser.c: In function '_nss_nisplus_parse_pwent':
nss_nisplus/nisplus-parser.c:90:7: error: 'strncpy' destination unchanged after copying no bytes [-Werror=stringop-truncation]
       strncpy (first_unused, numstr, len);
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
nss_nisplus/nisplus-parser.c:106:7: error: 'strncpy' destination unchanged after copying no bytes [-Werror=stringop-truncation]
       strncpy (first_unused, numstr, len);
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

introduced with commit ac05397075f6:

commit ac05397075f621cfdbe1db527c96167a58b6d18e
Author: Ulrich Drepper <drepper@redhat.com>
Date:   Sun Apr 30 07:01:26 2006 +0000

	* nis/nss_nisplus/nisplus-parser.c: Minor optimizations and
	cleanups.  Avoid copying data if it can be used in the old place.

(no mailing list reference available).  Obviously regardless of the
recently added compiler diagnostics causing a build error this code has
been long non-functional, so I guess NIS+ servers have been supplying
strings that are non-empty and have already been null-terminated.
Which in turn made it unnecessary to make a null-terminated copy,
masking this bug.

	[BZ #23266]
	* nis/nss_nisplus/nisplus-parser.c (_nss_nisplus_parse_pwent):
	Copy and null-terminate entries that are not terminated, in
	addition to empty ones.
---
On Mon, 25 Jun 2018, DJ Delorie wrote:

> >  Ping for:
> >
> > <https://patchwork.sourceware.org/patch/27908/>
> >
> > Previous discussion:
> >
> > <https://patchwork.sourceware.org/patch/27906/>
> 
> LGTM

 Thanks, applied now, with two minor updates:

* s/compilation/build/ in the heading so that it fits in 79 columns with 
  GIT's indentation applied,

* a comma added after "are not terminated" in the description and 
  ChangeLog, for clarity,

which I have decided that qualify as trivial and therefore not requiring 
further consensus.

 Here's the actual version committed, for future reference.

  Maciej

---
 ChangeLog                        |    7 +++++++
 nis/nss_nisplus/nisplus-parser.c |    4 ++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/nis/nss_nisplus/nisplus-parser.c b/nis/nss_nisplus/nisplus-parser.c
index 8dc021e..d2b0633 100644
--- a/nis/nss_nisplus/nisplus-parser.c
+++ b/nis/nss_nisplus/nisplus-parser.c
@@ -82,7 +82,7 @@ _nss_nisplus_parse_pwent (nis_result *result, struct passwd *pw,
 
   char *numstr = NISOBJVAL (2, obj);
   len = NISOBJLEN (2, obj);
-  if (len == 0 && numstr[len - 1] != '\0')
+  if (len == 0 || numstr[len - 1] != '\0')
     {
       if (len >= room_left)
 	goto no_more_room;
@@ -98,7 +98,7 @@ _nss_nisplus_parse_pwent (nis_result *result, struct passwd *pw,
 
   numstr = NISOBJVAL (3, obj);
   len = NISOBJLEN (3, obj);
-  if (len == 0 && numstr[len - 1] != '\0')
+  if (len == 0 || numstr[len - 1] != '\0')
     {
       if (len >= room_left)
 	goto no_more_room;
-- 
1.7.2.5