o compat_group() and files_group() are more complicated than I thought

in rev. 1.34.  Mainly I missed the fact that the buffer is used for two
purposes:

1) storing a group line from the group file;

2) __gr_parse_entry() parses the buffer and tries to put the group
members to the remaining part of the buffer and can fail if there
is no enough room for them.

Re-arrange the buffer size checks to account the latter case.

Submitted by:	Kirk R Webb
MFC after:	2 weeks

1 files changed, 6 insertions, 4 deletions

diff --git a/lib/libc/gen/getgrent.c b/lib/libc/gen/getgrent.c
index 511edddc0626..714433ebe4b9 100644
--- a/lib/libc/gen/getgrent.c
+++ b/lib/libc/gen/getgrent.c
@@ -770,18 +770,17 @@ files_group(void *retval, void *mdata, va_list ap)
 		 * pointer for the member list terminator.
 		 */
 		if (bufsize <= linesize + _ALIGNBYTES + sizeof(char *)) {
-			fseeko(st->fp, pos, SEEK_SET);
 			*errnop = ERANGE;
 			rv = NS_RETURN;
 			break;
 		}
-		pos = ftello(st->fp);
 		memcpy(buffer, line, linesize);
 		buffer[linesize] = '\0';
 		rv = __gr_parse_entry(buffer, linesize, grp, 
 		    &buffer[linesize + 1], bufsize - linesize - 1, errnop);
 		if (rv & NS_TERMINATE)
 			break;
+		pos = ftello(st->fp);
 	}
 	if (!stayopen && st->fp != NULL) {
 		fclose(st->fp);
@@ -789,6 +788,8 @@ files_group(void *retval, void *mdata, va_list ap)
 	}
 	if (rv == NS_SUCCESS && retval != NULL)
 		*(struct group **)retval = grp;
+	else if (*errnop == ERANGE)
+		fseeko(st->fp, pos, SEEK_SET);
 	return (rv);
 }
 
@@ -1322,18 +1323,17 @@ docompat:
 		 * pointer for the member list terminator.
 		 */
 		if (bufsize <= linesize + _ALIGNBYTES + sizeof(char *)) {
-			fseeko(st->fp, pos, SEEK_SET);
 			*errnop = ERANGE;
 			rv = NS_RETURN;
 			break;
 		}
-		pos = ftello(st->fp);
 		memcpy(buffer, line, linesize);
 		buffer[linesize] = '\0';
 		rv = __gr_parse_entry(buffer, linesize, grp, 
 		    &buffer[linesize + 1], bufsize - linesize - 1, errnop);
 		if (rv & NS_TERMINATE)
 			break;
+		pos = ftello(st->fp);
 	}
 fin:
 	if (!stayopen && st->fp != NULL) {
@@ -1342,6 +1342,8 @@ fin:
 	}
 	if (rv == NS_SUCCESS && retval != NULL)
 		*(struct group **)retval = grp;
+	else if (*errnop == ERANGE)
+		fseeko(st->fp, pos, SEEK_SET);
 	return (rv);
 #undef set_lookup_type
 }