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author | 2023-11-13 21:13:23 +0100 | |
---|---|---|
committer | 2023-11-14 16:16:21 +0100 | |
commit | 28628fa952fefc7f2072ce6e8016968cc452b1ba (patch) | |
tree | 08f7350333f21b8edb207b37e435b66b7214d0c8 | |
parent | netfilter: nf_tables: bogus ENOENT when destroying element which does not exist (diff) | |
download | linux-28628fa952fefc7f2072ce6e8016968cc452b1ba.tar.gz linux-28628fa952fefc7f2072ce6e8016968cc452b1ba.tar.bz2 linux-28628fa952fefc7f2072ce6e8016968cc452b1ba.zip |
netfilter: ipset: fix race condition between swap/destroy and kernel side add/del/test
Linkui Xiao reported that there's a race condition when ipset swap and destroy is
called, which can lead to crash in add/del/test element operations. Swap then
destroy are usual operations to replace a set with another one in a production
system. The issue can in some cases be reproduced with the script:
ipset create hash_ip1 hash:net family inet hashsize 1024 maxelem 1048576
ipset add hash_ip1 172.20.0.0/16
ipset add hash_ip1 192.168.0.0/16
iptables -A INPUT -m set --match-set hash_ip1 src -j ACCEPT
while [ 1 ]
do
# ... Ongoing traffic...
ipset create hash_ip2 hash:net family inet hashsize 1024 maxelem 1048576
ipset add hash_ip2 172.20.0.0/16
ipset swap hash_ip1 hash_ip2
ipset destroy hash_ip2
sleep 0.05
done
In the race case the possible order of the operations are
CPU0 CPU1
ip_set_test
ipset swap hash_ip1 hash_ip2
ipset destroy hash_ip2
hash_net_kadt
Swap replaces hash_ip1 with hash_ip2 and then destroy removes hash_ip2 which
is the original hash_ip1. ip_set_test was called on hash_ip1 and because destroy
removed it, hash_net_kadt crashes.
The fix is to force ip_set_swap() to wait for all readers to finish accessing the
old set pointers by calling synchronize_rcu().
The first version of the patch was written by Linkui Xiao <xiaolinkui@kylinos.cn>.
v2: synchronize_rcu() is moved into ip_set_swap() in order not to burden
ip_set_destroy() unnecessarily when all sets are destroyed.
v3: Florian Westphal pointed out that all netfilter hooks run with rcu_read_lock() held
and em_ipset.c wraps the entire ip_set_test() in rcu read lock/unlock pair.
So there's no need to extend the rcu read locked area in ipset itself.
Closes: https://lore.kernel.org/all/69e7963b-e7f8-3ad0-210-7b86eebf7f78@netfilter.org/
Reported by: Linkui Xiao <xiaolinkui@kylinos.cn>
Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
-rw-r--r-- | net/netfilter/ipset/ip_set_core.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c index 35d2f9c9ada0..4c133e06be1d 100644 --- a/net/netfilter/ipset/ip_set_core.c +++ b/net/netfilter/ipset/ip_set_core.c @@ -61,6 +61,8 @@ MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_IPSET); ip_set_dereference((inst)->ip_set_list)[id] #define ip_set_ref_netlink(inst,id) \ rcu_dereference_raw((inst)->ip_set_list)[id] +#define ip_set_dereference_nfnl(p) \ + rcu_dereference_check(p, lockdep_nfnl_is_held(NFNL_SUBSYS_IPSET)) /* The set types are implemented in modules and registered set types * can be found in ip_set_type_list. Adding/deleting types is @@ -708,15 +710,10 @@ __ip_set_put_netlink(struct ip_set *set) static struct ip_set * ip_set_rcu_get(struct net *net, ip_set_id_t index) { - struct ip_set *set; struct ip_set_net *inst = ip_set_pernet(net); - rcu_read_lock(); - /* ip_set_list itself needs to be protected */ - set = rcu_dereference(inst->ip_set_list)[index]; - rcu_read_unlock(); - - return set; + /* ip_set_list and the set pointer need to be protected */ + return ip_set_dereference_nfnl(inst->ip_set_list)[index]; } static inline void @@ -1397,6 +1394,9 @@ static int ip_set_swap(struct sk_buff *skb, const struct nfnl_info *info, ip_set(inst, to_id) = from; write_unlock_bh(&ip_set_ref_lock); + /* Make sure all readers of the old set pointers are completed. */ + synchronize_rcu(); + return 0; } |