netdev - [PATCH] net: check for NULL net

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Message-Id: <1467636446-6771-1-git-send-email-vegard.nossum@oracle.com>
Date:	Mon,  4 Jul 2016 14:47:26 +0200
From:	Vegard Nossum <vegard.nossum@...cle.com>
To:	Andy Gospodarek <gospo@...ulusnetworks.com>, davem@...emloft.net
Cc:	netdev@...r.kernel.org, Vegard Nossum <vegard.nossum@...cle.com>,
	Dinesh Dutt <ddutt@...ulusnetworks.com>,
	Scott Feldman <sfeldma@...il.com>
Subject: [PATCH] net: check for NULL net_device in FIB tables

struct fib_nh->nh_dev can be NULL, so we should check it before calling
__in_dev_get_rcu on it.

Multiple places seem to want this (and check the return value), so we can
add a convenience wrapper for this.

This fixes a crash in AF_NETLINK sendmsg().

Please double check that I caught all the callers that need the NULL
guard.

Fixes: 0eeb075fad73 ("net: ipv4 sysctl option to ignore routes when nexthop link is down")
Cc: Andy Gospodarek <gospo@...ulusnetworks.com>
Cc: Dinesh Dutt <ddutt@...ulusnetworks.com>
Cc: Scott Feldman <sfeldma@...il.com>
Cc: David S. Miller <davem@...emloft.net>
Signed-off-by: Vegard Nossum <vegard.nossum@...cle.com>
---
 include/linux/inetdevice.h | 7 +++++++
 net/ipv4/fib_semantics.c   | 8 ++++----
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index ee971f3..2d8bea1 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -222,6 +222,13 @@ static inline struct in_device *__in_dev_get_rtnl(const struct net_device *dev)
 	return rtnl_dereference(dev->ip_ptr);
 }
 
+static inline struct in_device *in_dev_get_rtnl(const struct net_device *dev)
+{
+	if (!dev)
+		return NULL;
+	return __in_dev_get_rtnl(dev);
+}
+
 static inline struct neigh_parms *__in_dev_arp_parms_get_rcu(const struct net_device *dev)
 {
 	struct in_device *in_dev = __in_dev_get_rcu(dev);
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index d09173b..8289799 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -545,7 +545,7 @@ static void fib_rebalance(struct fib_info *fi)
 		if (nh->nh_flags & RTNH_F_DEAD)
 			continue;
 
-		in_dev = __in_dev_get_rtnl(nh->nh_dev);
+		in_dev = in_dev_get_rtnl(nh->nh_dev);
 
 		if (in_dev &&
 		    IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&
@@ -559,7 +559,7 @@ static void fib_rebalance(struct fib_info *fi)
 	change_nexthops(fi) {
 		int upper_bound;
 
-		in_dev = __in_dev_get_rtnl(nexthop_nh->nh_dev);
+		in_dev = in_dev_get_rtnl(nexthop_nh->nh_dev);
 
 		if (nexthop_nh->nh_flags & RTNH_F_DEAD) {
 			upper_bound = -1;
@@ -1261,7 +1261,7 @@ int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event,
 		    nla_put_u32(skb, RTA_OIF, fi->fib_nh->nh_oif))
 			goto nla_put_failure;
 		if (fi->fib_nh->nh_flags & RTNH_F_LINKDOWN) {
-			in_dev = __in_dev_get_rtnl(fi->fib_nh->nh_dev);
+			in_dev = in_dev_get_rtnl(fi->fib_nh->nh_dev);
 			if (in_dev &&
 			    IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev))
 				rtm->rtm_flags |= RTNH_F_DEAD;
@@ -1292,7 +1292,7 @@ int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event,
 
 			rtnh->rtnh_flags = nh->nh_flags & 0xFF;
 			if (nh->nh_flags & RTNH_F_LINKDOWN) {
-				in_dev = __in_dev_get_rtnl(nh->nh_dev);
+				in_dev = in_dev_get_rtnl(nh->nh_dev);
 				if (in_dev &&
 				    IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev))
 					rtnh->rtnh_flags |= RTNH_F_DEAD;
-- 
1.9.1