Add an ip_fib fix that we missed

After commit b427832009b9 "net: ipv4: update fnhe_pmtu when first
hop's MTU changes", sparse complained:

net/ipv4/fib_semantics.c:1140:18: sparse: incompatible types in comparison expression (different address spaces)

which revealed that we missed this fix.

2 files changed, 84 insertions, 0 deletions

diff --git a/queue-3.16/ipv4-fix-a-race-in-update_or_create_fnhe.patch b/queue-3.16/ipv4-fix-a-race-in-update_or_create_fnhe.patch
new file mode 100644
index 00000000..0357fc5d
--- /dev/null
+++ b/queue-3.16/ipv4-fix-a-race-in-update_or_create_fnhe.patch
@@ -0,0 +1,83 @@
+From: Eric Dumazet <edumazet@google.com>
+Date: Wed, 3 Sep 2014 22:21:56 -0700
+Subject: ipv4: fix a race in update_or_create_fnhe()
+
+commit caa415270c732505240bb60171c44a7838c555e8 upstream.
+
+nh_exceptions is effectively used under rcu, but lacks proper
+barriers. Between kzalloc() and setting of nh->nh_exceptions(),
+we need a proper memory barrier.
+
+Signed-off-by: Eric Dumazet <edumazet@google.com>
+Fixes: 4895c771c7f00 ("ipv4: Add FIB nexthop exceptions.")
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
+---
+ include/net/ip_fib.h     | 2 +-
+ net/ipv4/fib_semantics.c | 8 +++++---
+ net/ipv4/route.c         | 6 +++---
+ 3 files changed, 9 insertions(+), 7 deletions(-)
+
+--- a/include/net/ip_fib.h
++++ b/include/net/ip_fib.h
+@@ -89,7 +89,7 @@ struct fib_nh {
+ 	int			nh_saddr_genid;
+ 	struct rtable __rcu * __percpu *nh_pcpu_rth_output;
+ 	struct rtable __rcu	*nh_rth_input;
+-	struct fnhe_hash_bucket	*nh_exceptions;
++	struct fnhe_hash_bucket	__rcu *nh_exceptions;
+ };
+ 
+ /*
+--- a/net/ipv4/fib_semantics.c
++++ b/net/ipv4/fib_semantics.c
+@@ -157,9 +157,12 @@ static void rt_fibinfo_free(struct rtabl
+ 
+ static void free_nh_exceptions(struct fib_nh *nh)
+ {
+-	struct fnhe_hash_bucket *hash = nh->nh_exceptions;
++	struct fnhe_hash_bucket *hash;
+ 	int i;
+ 
++	hash = rcu_dereference_protected(nh->nh_exceptions, 1);
++	if (!hash)
++		return;
+ 	for (i = 0; i < FNHE_HASH_SIZE; i++) {
+ 		struct fib_nh_exception *fnhe;
+ 
+@@ -206,8 +209,7 @@ static void free_fib_info_rcu(struct rcu
+ 	change_nexthops(fi) {
+ 		if (nexthop_nh->nh_dev)
+ 			dev_put(nexthop_nh->nh_dev);
+-		if (nexthop_nh->nh_exceptions)
+-			free_nh_exceptions(nexthop_nh);
++		free_nh_exceptions(nexthop_nh);
+ 		rt_fibinfo_free_cpus(nexthop_nh->nh_pcpu_rth_output);
+ 		rt_fibinfo_free(&nexthop_nh->nh_rth_input);
+ 	} endfor_nexthops(fi);
+--- a/net/ipv4/route.c
++++ b/net/ipv4/route.c
+@@ -635,12 +635,12 @@ static void update_or_create_fnhe(struct
+ 
+ 	spin_lock_bh(&fnhe_lock);
+ 
+-	hash = nh->nh_exceptions;
++	hash = rcu_dereference(nh->nh_exceptions);
+ 	if (!hash) {
+ 		hash = kzalloc(FNHE_HASH_SIZE * sizeof(*hash), GFP_ATOMIC);
+ 		if (!hash)
+ 			goto out_unlock;
+-		nh->nh_exceptions = hash;
++		rcu_assign_pointer(nh->nh_exceptions, hash);
+ 	}
+ 
+ 	hash += hval;
+@@ -1293,7 +1293,7 @@ static void ip_del_fnhe(struct fib_nh *n
+ 
+ static struct fib_nh_exception *find_exception(struct fib_nh *nh, __be32 daddr)
+ {
+-	struct fnhe_hash_bucket *hash = nh->nh_exceptions;
++	struct fnhe_hash_bucket *hash = rcu_dereference(nh->nh_exceptions);
+ 	struct fib_nh_exception *fnhe;
+ 	u32 hval;
+ 
diff --git a/queue-3.16/series b/queue-3.16/series
index 2c085405..4fa59399 100644
--- a/queue-3.16/series
+++ b/queue-3.16/series
@@ -3,3 +3,4 @@ brcmfmac-add-length-checks-in-scheduled-scan-result-handler.patch
 inet-update-the-ip-id-generation-algorithm-to-higher-standards.patch
 spi-omap-100k-remove-unused-definitions.patch
 vxlan-fix-big-endian-declaration-of-vni.patch
+ipv4-fix-a-race-in-update_or_create_fnhe.patch