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netfilter: conntrack: protect early_drop by rcu read lock 

User can add ct entry via nfnetlink(IPCTNL_MSG_CT_NEW), and if the total
number reach the nf_conntrack_max, we will try to drop some ct entries.

But in this case(the main function call path is ctnetlink_create_conntrack
-> nf_conntrack_alloc -> early_drop), rcu_read_lock is not held, so race
with hash resize will happen.

Fixes: 242922a027 ("netfilter: conntrack: simplify early_drop")
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Liping Zhang 2016-07-12 19:45:00 +08:00 committed by Pablo Neira Ayuso
parent c2b9b4fee8
commit 3101e0fc1f
1 changed files with 3 additions and 0 deletions
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3
net/netfilter/nf_conntrack_core.c
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@ -880,6 +880,7 @@ static noinline int early_drop(struct net *net, unsigned int _hash)
struct hlist_nulls_head *ct_hash;
unsigned hash, sequence, drops;
rcu_read_lock();
do {
sequence = read_seqcount_begin(&nf_conntrack_generation);
hash = scale_hash(_hash++);
@ -887,6 +888,8 @@ static noinline int early_drop(struct net *net, unsigned int _hash)
} while (read_seqcount_retry(&nf_conntrack_generation, sequence));
drops = early_drop_list(net, &ct_hash[hash]);
rcu_read_unlock();
if (drops) {
NF_CT_STAT_ADD_ATOMIC(net, early_drop, drops);
return true;