[src/trunk]: src/sys/net Synchronize on rtcache_generation with rtlock

[ozaki-r <ozaki-r%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/59da79de7752
branches:  trunk
changeset: 356428:59da79de7752
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Mon Sep 25 04:15:33 2017 +0000

description:
Synchronize on rtcache_generation with rtlock

It's racy if NET_MPSAFE is enabled.

Pointed out by joerg@

diffstat:

 sys/net/route.c |  19 ++++++++++++-------
 1 files changed, 12 insertions(+), 7 deletions(-)

diffs (82 lines):

diff -r a38f0a596336 -r 59da79de7752 sys/net/route.c
--- a/sys/net/route.c   Mon Sep 25 01:57:54 2017 +0000
+++ b/sys/net/route.c   Mon Sep 25 04:15:33 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: route.c,v 1.200 2017/09/22 05:05:32 ozaki-r Exp $      */
+/*     $NetBSD: route.c,v 1.201 2017/09/25 04:15:33 ozaki-r Exp $      */
 
 /*-
  * Copyright (c) 1998, 2008 The NetBSD Foundation, Inc.
@@ -97,7 +97,7 @@
 #endif
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: route.c,v 1.200 2017/09/22 05:05:32 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: route.c,v 1.201 2017/09/25 04:15:33 ozaki-r Exp $");
 
 #include <sys/param.h>
 #ifdef RTFLUSH_DEBUG
@@ -484,6 +484,8 @@
 rtcache_invalidate(void)
 {
 
+       RT_ASSERT_WLOCK();
+
        if (rtcache_debug())
                printf("%s: enter\n", __func__);
 
@@ -1199,10 +1201,10 @@
                        rt_ref(rt);
                        RT_REFCNT_TRACE(rt);
                }
+               rtcache_invalidate();
                RT_UNLOCK();
                need_unlock = false;
                rt_timer_remove_all(rt);
-               rtcache_invalidate();
 #if defined(INET) || defined(INET6)
                if (netmask != NULL)
                        lltable_prefix_free(dst->sa_family, dst, netmask, 0);
@@ -1295,9 +1297,9 @@
                        rt_ref(rt);
                        RT_REFCNT_TRACE(rt);
                }
+               rtcache_invalidate();
                RT_UNLOCK();
                need_unlock = false;
-               rtcache_invalidate();
                break;
        case RTM_GET:
                if (netmask != NULL) {
@@ -1898,8 +1900,10 @@
        if (ret != 0)
                goto out;
 
+       RT_RLOCK();
        new_ro->_ro_rt = rt;
        new_ro->ro_rtcache_generation = rtcache_generation;
+       RT_UNLOCK();
        rtcache_invariants(new_ro);
 out:
        rtcache_unref(rt, old_ro);
@@ -1957,16 +1961,17 @@
 retry:
 #endif
        rtcache_invariants(ro);
+       RT_RLOCK();
        if (ro->ro_rtcache_generation != rtcache_generation) {
                /* The cache is invalidated */
-               return NULL;
+               rt = NULL;
+               goto out;
        }
 
        rt = ro->_ro_rt;
        if (rt == NULL)
-               return NULL;
+               goto out;
 
-       RT_RLOCK();
        if ((rt->rt_flags & RTF_UP) == 0) {
                rt = NULL;
                goto out;