[src/trunk]: src/sys/net Fix the net.ether.multicast sysctl. If there is no m...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/a316b18cc100
branches:  trunk
changeset: 829032:a316b18cc100
user:      maxv <maxv%NetBSD.org@localhost>
date:      Mon Jan 15 07:59:48 2018 +0000

description:
Fix the net.ether.multicast sysctl. If there is no multicast address
don't kmem_alloc(0) (which panics the kernel), and if the number of
multicast addresses has decreased don't copyout uninitialized kernel
data.

diffstat:

 sys/net/if_ethersubr.c |  19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diffs (46 lines):

diff -r 8bbfb082d9ff -r a316b18cc100 sys/net/if_ethersubr.c
--- a/sys/net/if_ethersubr.c    Mon Jan 15 07:20:10 2018 +0000
+++ b/sys/net/if_ethersubr.c    Mon Jan 15 07:59:48 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_ethersubr.c,v 1.250 2017/12/09 10:51:30 maxv Exp $  */
+/*     $NetBSD: if_ethersubr.c,v 1.251 2018/01/15 07:59:48 maxv Exp $  */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -61,7 +61,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_ethersubr.c,v 1.250 2017/12/09 10:51:30 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_ethersubr.c,v 1.251 2018/01/15 07:59:48 maxv Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -1553,16 +1553,23 @@
 
        /*
         * ec->ec_lock is a spin mutex so we cannot call sysctl_copyout, which
-        * is sleepable, with holding it. Copy data to a local buffer first
-        * with holding it and then call sysctl_copyout without holding it.
+        * is sleepable, while holding it. Copy data to a local buffer first
+        * with the lock taken and then call sysctl_copyout without holding it.
         */
 retry:
        multicnt = ec->ec_multicnt;
+
+       if (multicnt == 0) {
+               if_put(ifp, &psref);
+               *oldlenp = 0;
+               goto out;
+       }
+
        addrs = kmem_alloc(sizeof(*addrs) * multicnt, KM_SLEEP);
 
        ETHER_LOCK(ec);
-       if (multicnt < ec->ec_multicnt) {
-               /* The number of multicast addresses have increased */
+       if (multicnt != ec->ec_multicnt) {
+               /* The number of multicast addresses has changed */
                ETHER_UNLOCK(ec);
                kmem_free(addrs, sizeof(*addrs) * multicnt);
                goto retry;