[NETFILTER]: ip_conntrack: fix NAT helper unload races
The NAT helpr hooks are protected by RCU, but all of the
conntrack helpers test and use the global pointers instead
of copying them first using rcu_dereference()
Also replace synchronize_net() by synchronize_rcu() for clarity
since sychronizing only with packet receive processing is
insufficient to prevent races.
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
index 05cb78c..2d23501 100644
--- a/net/netfilter/nf_conntrack_ftp.c
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -369,9 +369,9 @@
struct ip_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
struct nf_conntrack_expect *exp;
struct nf_conntrack_man cmd = {};
-
unsigned int i;
int found = 0, ends_in_nl;
+ typeof(nf_nat_ftp_hook) nf_nat_ftp;
/* Until there's been traffic both ways, don't look in packets. */
if (ctinfo != IP_CT_ESTABLISHED
@@ -520,9 +520,10 @@
/* Now, NAT might want to mangle the packet, and register the
* (possibly changed) expectation itself. */
- if (nf_nat_ftp_hook)
- ret = nf_nat_ftp_hook(pskb, ctinfo, search[dir][i].ftptype,
- matchoff, matchlen, exp, &seq);
+ nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
+ if (nf_nat_ftp)
+ ret = nf_nat_ftp(pskb, ctinfo, search[dir][i].ftptype,
+ matchoff, matchlen, exp, &seq);
else {
/* Can't expect this? Best to drop packet now. */
if (nf_conntrack_expect_related(exp) != 0)