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ipv4: fix a race in update_or_create_fnhe()

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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: 4895c771c7 ("ipv4: Add FIB nexthop exceptions.")
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2014-09-03 22:21:56 -07:00 committed by David S. Miller
parent 29abe2fda5
commit caa415270c
3 changed files with 9 additions and 7 deletions
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2
include/net/ip_fib.h
View File

@ -87,7 +87,7 @@ struct fib_nh {
int nh_saddr_genid; int nh_saddr_genid;
struct rtable __rcu * __percpu *nh_pcpu_rth_output; struct rtable __rcu * __percpu *nh_pcpu_rth_output;
struct rtable __rcu *nh_rth_input; struct rtable __rcu *nh_rth_input;
struct fnhe_hash_bucket *nh_exceptions; struct fnhe_hash_bucket __rcu *nh_exceptions;
}; };
/* /*

8
net/ipv4/fib_semantics.c
View File

@ -157,9 +157,12 @@ static void rt_fibinfo_free(struct rtable __rcu **rtp)
static void free_nh_exceptions(struct fib_nh *nh) static void free_nh_exceptions(struct fib_nh *nh)
{ {
struct fnhe_hash_bucket *hash = nh->nh_exceptions; struct fnhe_hash_bucket *hash;
int i; int i;
hash = rcu_dereference_protected(nh->nh_exceptions, 1);
if (!hash)
return;
for (i = 0; i < FNHE_HASH_SIZE; i++) { for (i = 0; i < FNHE_HASH_SIZE; i++) {
struct fib_nh_exception *fnhe; struct fib_nh_exception *fnhe;
@ -205,8 +208,7 @@ static void free_fib_info_rcu(struct rcu_head *head)
change_nexthops(fi) { change_nexthops(fi) {
if (nexthop_nh->nh_dev) if (nexthop_nh->nh_dev)
dev_put(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_cpus(nexthop_nh->nh_pcpu_rth_output);
rt_fibinfo_free(&nexthop_nh->nh_rth_input); rt_fibinfo_free(&nexthop_nh->nh_rth_input);
} endfor_nexthops(fi); } endfor_nexthops(fi);

6
net/ipv4/route.c
View File

@ -628,12 +628,12 @@ static void update_or_create_fnhe(struct fib_nh *nh, __be32 daddr, __be32 gw,
spin_lock_bh(&fnhe_lock); spin_lock_bh(&fnhe_lock);
hash = nh->nh_exceptions; hash = rcu_dereference(nh->nh_exceptions);
if (!hash) { if (!hash) {
hash = kzalloc(FNHE_HASH_SIZE * sizeof(*hash), GFP_ATOMIC); hash = kzalloc(FNHE_HASH_SIZE * sizeof(*hash), GFP_ATOMIC);
if (!hash) if (!hash)
goto out_unlock; goto out_unlock;
nh->nh_exceptions = hash; rcu_assign_pointer(nh->nh_exceptions, hash);
} }
hash += hval; hash += hval;
@ -1242,7 +1242,7 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst)
static struct fib_nh_exception *find_exception(struct fib_nh *nh, __be32 daddr) 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; struct fib_nh_exception *fnhe;
u32 hval; u32 hval;