kmem readable kvm db

[Ted Unangst]

The kvm_bsd.db file only needs to be readable by programs that are
setgid kmem. This is not much of an info leak since any user can read
/bsd (or in many cases download a copy), but moving forward it would
be nice to patch these leaks up one by one.

A few kmem grovelers appear to still work afterwards.

Index: kvm_mkdb.c
===================================================================
RCS file: /cvs/src/usr.sbin/kvm_mkdb/kvm_mkdb.c,v
retrieving revision 1.18
diff -u -p -r1.18 kvm_mkdb.c
--- kvm_mkdb.c  20 Jul 2014 01:38:40 -0000      1.18
+++ kvm_mkdb.c  16 Dec 2014 19:22:54 -0000
@@ -31,6 +31,9 @@
 
 #include <sys/param.h>
 #include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/resource.h>
 
 #include <db.h>
 #include <err.h>
@@ -42,10 +45,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-
-#include <sys/types.h>
-#include <sys/time.h>
-#include <sys/resource.h>
+#include <grp.h>
 
 #include "extern.h"
 
@@ -131,6 +131,7 @@ kvm_mkdb(int fd, const char *dbdir, char
        DB *db;
        char dbtemp[MAXPATHLEN], dbname[MAXPATHLEN];
        int r;
+       struct group *gr;
 
        r = snprintf(dbtemp, sizeof(dbtemp), "%skvm_%s.tmp",
            dbdir, nlistname);
@@ -155,7 +156,7 @@ kvm_mkdb(int fd, const char *dbdir, char
 
        (void)umask(0);
        db = dbopen(dbtemp, O_CREAT | O_EXLOCK | O_TRUNC | O_RDWR,
-           S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH, DB_HASH, &openinfo);
+           S_IRUSR | S_IWUSR | S_IRGRP, DB_HASH, &openinfo);
        if (db == NULL) {
                warn("can't dbopen %s", dbtemp);
                return(1);
@@ -167,6 +168,14 @@ kvm_mkdb(int fd, const char *dbdir, char
        }
        if (db->close(db)) {
                warn("can't dbclose %s", dbtemp);
+               (void)unlink(dbtemp);
+               return(1);
+       }
+
+       if ((gr = getgrnam("kmem")) == NULL) {
+               warn("can't find kmem group");
+       } else if (chown(dbtemp, -1, gr->gr_gid)) {
+               warn("can't chown %s", dbtemp);
                (void)unlink(dbtemp);
                return(1);
        }