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Date:      Fri, 7 Dec 2018 09:39:38 +0000 (UTC)
From:      "Andrey V. Elsukov" <ae@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org
Subject:   svn commit: r341678 - stable/11/sys/net
Message-ID:  <201812070939.wB79dcKM060018@repo.freebsd.org>
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Author: ae
Date: Fri Dec  7 09:39:37 2018
New Revision: 341678
URL: https://svnweb.freebsd.org/changeset/base/341678

Log:
  MFC r341008:
    Fix possible panic during ifnet detach in rtsock.
  
    The panic can happen, when some application does dump of routing table
    using sysctl interface. To prevent this, set IFF_DYING flag in
    if_detach_internal() function, when ifnet under lock is removed from
    the chain. In sysctl_rtsock() take IFNET_RLOCK_NOSLEEP() to prevent
    ifnet detach during routes enumeration. In case, if some interface was
    detached in the time before we take the lock, add the check, that ifnet
    is not DYING. This prevents access to memory that could be freed after
    ifnet is unlinked.
  
    Differential Revision:	https://reviews.freebsd.org/D18338

Modified:
  stable/11/sys/net/if.c
  stable/11/sys/net/rtsock.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/net/if.c
==============================================================================
--- stable/11/sys/net/if.c	Fri Dec  7 09:38:25 2018	(r341677)
+++ stable/11/sys/net/if.c	Fri Dec  7 09:39:37 2018	(r341678)
@@ -1031,6 +1031,8 @@ if_detach_internal(struct ifnet *ifp, int vmove, struc
 	TAILQ_FOREACH(iter, &V_ifnet, if_link)
 		if (iter == ifp) {
 			TAILQ_REMOVE(&V_ifnet, ifp, if_link);
+			if (!vmove)
+				ifp->if_flags |= IFF_DYING;
 			found = 1;
 			break;
 		}

Modified: stable/11/sys/net/rtsock.c
==============================================================================
--- stable/11/sys/net/rtsock.c	Fri Dec  7 09:38:25 2018	(r341677)
+++ stable/11/sys/net/rtsock.c	Fri Dec  7 09:39:37 2018	(r341678)
@@ -1548,6 +1548,8 @@ sysctl_dumpentry(struct radix_node *rn, void *vw)
 	struct rt_addrinfo info;
 	struct sockaddr_storage ss;
 
+	IFNET_RLOCK_NOSLEEP_ASSERT();
+
 	if (w->w_op == NET_RT_FLAGS && !(rt->rt_flags & w->w_arg))
 		return 0;
 	if ((rt->rt_flags & RTF_HOST) == 0
@@ -1560,7 +1562,7 @@ sysctl_dumpentry(struct radix_node *rn, void *vw)
 	info.rti_info[RTAX_NETMASK] = rtsock_fix_netmask(rt_key(rt),
 	    rt_mask(rt), &ss);
 	info.rti_info[RTAX_GENMASK] = 0;
-	if (rt->rt_ifp) {
+	if (rt->rt_ifp && !(rt->rt_ifp->if_flags & IFF_DYING)) {
 		info.rti_info[RTAX_IFP] = rt->rt_ifp->if_addr->ifa_addr;
 		info.rti_info[RTAX_IFA] = rt->rt_ifa->ifa_addr;
 		if (rt->rt_ifp->if_flags & IFF_POINTOPOINT)
@@ -1925,8 +1927,10 @@ sysctl_rtsock(SYSCTL_HANDLER_ARGS)
 			rnh = rt_tables_get_rnh(fib, i);
 			if (rnh != NULL) {
 				RIB_RLOCK(rnh); 
+				IFNET_RLOCK_NOSLEEP();
 			    	error = rnh->rnh_walktree(&rnh->head,
 				    sysctl_dumpentry, &w);
+				IFNET_RUNLOCK_NOSLEEP();
 				RIB_RUNLOCK(rnh);
 			} else if (af != 0)
 				error = EAFNOSUPPORT;

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