[NETFILTER]: nf_conntrack: fix helper module unload races
When a helper module is unloaded all conntracks refering to it have their
helper pointer NULLed out, leading to lots of races. In most places this
can be fixed by proper use of RCU (they do already check for != NULL,
but in a racy way), additionally nf_conntrack_expect_related needs to
bail out when no helper is present.
Also remove two paranoid BUG_ONs in nf_conntrack_proto_gre that are racy
and not worth fixing.
Signed-off-by: Patrick McHarrdy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 483e927..7a15e30 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -350,9 +350,15 @@
{
struct nf_conn *ct = (void *)ul_conntrack;
struct nf_conn_help *help = nfct_help(ct);
+ struct nf_conntrack_helper *helper;
- if (help && help->helper && help->helper->destroy)
- help->helper->destroy(ct);
+ if (help) {
+ rcu_read_lock();
+ helper = rcu_dereference(help->helper);
+ if (helper && helper->destroy)
+ helper->destroy(ct);
+ rcu_read_unlock();
+ }
write_lock_bh(&nf_conntrack_lock);
/* Inside lock so preempt is disabled on module removal path.
@@ -661,6 +667,7 @@
unsigned int dataoff)
{
struct nf_conn *conntrack;
+ struct nf_conn_help *help;
struct nf_conntrack_tuple repl_tuple;
struct nf_conntrack_expect *exp;
u_int32_t features = 0;
@@ -691,6 +698,7 @@
write_lock_bh(&nf_conntrack_lock);
exp = find_expectation(tuple);
+ help = nfct_help(conntrack);
if (exp) {
DEBUGP("conntrack: expectation arrives ct=%p exp=%p\n",
conntrack, exp);
@@ -698,7 +706,7 @@
__set_bit(IPS_EXPECTED_BIT, &conntrack->status);
conntrack->master = exp->master;
if (exp->helper)
- nfct_help(conntrack)->helper = exp->helper;
+ rcu_assign_pointer(help->helper, exp->helper);
#ifdef CONFIG_NF_CONNTRACK_MARK
conntrack->mark = exp->master->mark;
#endif
@@ -708,10 +716,11 @@
nf_conntrack_get(&conntrack->master->ct_general);
NF_CT_STAT_INC(expect_new);
} else {
- struct nf_conn_help *help = nfct_help(conntrack);
-
- if (help)
- help->helper = __nf_ct_helper_find(&repl_tuple);
+ if (help) {
+ /* not in hash table yet, so not strictly necessary */
+ rcu_assign_pointer(help->helper,
+ __nf_ct_helper_find(&repl_tuple));
+ }
NF_CT_STAT_INC(new);
}
@@ -893,7 +902,8 @@
helper = __nf_ct_helper_find(newreply);
if (helper)
memset(&help->help, 0, sizeof(help->help));
- help->helper = helper;
+ /* not in hash table yet, so not strictly necessary */
+ rcu_assign_pointer(help->helper, helper);
}
write_unlock_bh(&nf_conntrack_lock);
}