[src/trunk]: src/sys/net Fix race condition in sysctl_iflist

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

details:   https://anonhg.NetBSD.org/src/rev/1269d110f914
branches:  trunk
changeset: 822324:1269d110f914
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Tue Mar 14 08:11:09 2017 +0000

description:
Fix race condition in sysctl_iflist

We need to use psref for the ifa iteration because iflist_addr can sleep.

diffstat:

 sys/net/rtsock.c |  17 ++++++++++++++---
 1 files changed, 14 insertions(+), 3 deletions(-)

diffs (53 lines):

diff -r 40f9f3bad5f4 -r 1269d110f914 sys/net/rtsock.c
--- a/sys/net/rtsock.c  Tue Mar 14 08:09:31 2017 +0000
+++ b/sys/net/rtsock.c  Tue Mar 14 08:11:09 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: rtsock.c,v 1.204 2017/03/14 04:25:10 ozaki-r Exp $     */
+/*     $NetBSD: rtsock.c,v 1.205 2017/03/14 08:11:09 ozaki-r Exp $     */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -61,7 +61,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: rtsock.c,v 1.204 2017/03/14 04:25:10 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: rtsock.c,v 1.205 2017/03/14 08:11:09 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -1678,6 +1678,7 @@
 
        s = pserialize_read_enter();
        IFNET_READER_FOREACH(ifp) {
+               int _s;
                if (w->w_arg && w->w_arg != ifp->if_index)
                        continue;
                if (IFADDR_READER_EMPTY(ifp))
@@ -1694,15 +1695,25 @@
                        if ((error = iflist_if(ifp, w, &info, len)) != 0)
                                goto release_exit;
                }
+               _s = pserialize_read_enter();
                IFADDR_READER_FOREACH(ifa, ifp) {
+                       struct psref _psref;
                        if (af && af != ifa->ifa_addr->sa_family)
                                continue;
+                       ifa_acquire(ifa, &_psref);
+                       pserialize_read_exit(_s);
+
                        info.rti_info[RTAX_IFA] = ifa->ifa_addr;
                        info.rti_info[RTAX_NETMASK] = ifa->ifa_netmask;
                        info.rti_info[RTAX_BRD] = ifa->ifa_dstaddr;
-                       if ((error = iflist_addr(w, ifa, &info)) != 0)
+                       error = iflist_addr(w, ifa, &info);
+
+                       _s = pserialize_read_enter();
+                       ifa_release(ifa, &_psref);
+                       if (error != 0)
                                goto release_exit;
                }
+               pserialize_read_exit(_s);
                info.rti_info[RTAX_IFA] = info.rti_info[RTAX_NETMASK] =
                    info.rti_info[RTAX_BRD] = NULL;