2 files changed, 86 insertions, 1 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index b3cc318ceb45..76310940cbd7 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -876,6 +876,33 @@ static void __nf_conntrack_hash_insert(struct nf_conn *ct,
 			   &nf_conntrack_hash[reply_hash]);
 }
 
+static bool nf_ct_ext_valid_pre(const struct nf_ct_ext *ext)
+{
+	/* if ext->gen_id is not equal to nf_conntrack_ext_genid, some extensions
+	 * may contain stale pointers to e.g. helper that has been removed.
+	 *
+	 * The helper can't clear this because the nf_conn object isn't in
+	 * any hash and synchronize_rcu() isn't enough because associated skb
+	 * might sit in a queue.
+	 */
+	return !ext || ext->gen_id == atomic_read(&nf_conntrack_ext_genid);
+}
+
+static bool nf_ct_ext_valid_post(struct nf_ct_ext *ext)
+{
+	if (!ext)
+		return true;
+
+	if (ext->gen_id != atomic_read(&nf_conntrack_ext_genid))
+		return false;
+
+	/* inserted into conntrack table, nf_ct_iterate_cleanup()
+	 * will find it.  Disable nf_ct_ext_find() id check.
+	 */
+	WRITE_ONCE(ext->gen_id, 0);
+	return true;
+}
+
 int
 nf_conntrack_hash_check_insert(struct nf_conn *ct)
 {
@@ -891,6 +918,11 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct)
 
 	zone = nf_ct_zone(ct);
 
+	if (!nf_ct_ext_valid_pre(ct->ext)) {
+		NF_CT_STAT_INC(net, insert_failed);
+		return -ETIMEDOUT;
+	}
+
 	local_bh_disable();
 	do {
 		sequence = read_seqcount_begin(&nf_conntrack_generation);
@@ -931,6 +963,13 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct)
 	nf_conntrack_double_unlock(hash, reply_hash);
 	NF_CT_STAT_INC(net, insert);
 	local_bh_enable();
+
+	if (!nf_ct_ext_valid_post(ct->ext)) {
+		nf_ct_kill(ct);
+		NF_CT_STAT_INC(net, drop);
+		return -ETIMEDOUT;
+	}
+
 	return 0;
 chaintoolong:
 	NF_CT_STAT_INC(net, chaintoolong);
@@ -1198,6 +1237,11 @@ __nf_conntrack_confirm(struct sk_buff *skb)
 		return NF_DROP;
 	}
 
+	if (!nf_ct_ext_valid_pre(ct->ext)) {
+		NF_CT_STAT_INC(net, insert_failed);
+		goto dying;
+	}
+
 	pr_debug("Confirming conntrack %p\n", ct);
 	/* We have to check the DYING flag after unlink to prevent
 	 * a race against nf_ct_get_next_corpse() possibly called from
@@ -1254,6 +1298,16 @@ chaintoolong:
 	nf_conntrack_double_unlock(hash, reply_hash);
 	local_bh_enable();
 
+	/* ext area is still valid (rcu read lock is held,
+	 * but will go out of scope soon, we need to remove
+	 * this conntrack again.
+	 */
+	if (!nf_ct_ext_valid_post(ct->ext)) {
+		nf_ct_kill(ct);
+		NF_CT_STAT_INC(net, drop);
+		return NF_DROP;
+	}
+
 	help = nfct_help(ct);
 	if (help && help->helper)
 		nf_conntrack_event_cache(IPCT_HELPER, ct);
@@ -2491,6 +2545,7 @@ nf_ct_iterate_destroy(int (*iter)(struct nf_conn *i, void *data), void *data)
 	 */
 	synchronize_net();
 
+	nf_ct_ext_bump_genid();
 	nf_ct_iterate_cleanup(iter, data, 0, 0);
 }
 EXPORT_SYMBOL_GPL(nf_ct_iterate_destroy);
diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
index 1296fda54ac6..0b513f7bf9f3 100644
--- a/net/netfilter/nf_conntrack_extend.c
+++ b/net/netfilter/nf_conntrack_extend.c
@@ -27,6 +27,8 @@
 
 #define NF_CT_EXT_PREALLOC	128u /* conntrack events are on by default */
 
+atomic_t nf_conntrack_ext_genid __read_mostly = ATOMIC_INIT(1);
+
 static const u8 nf_ct_ext_type_len[NF_CT_EXT_NUM] = {
 	[NF_CT_EXT_HELPER] = sizeof(struct nf_conn_help),
 #if IS_ENABLED(CONFIG_NF_NAT)
@@ -116,8 +118,10 @@ void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
 	if (!new)
 		return NULL;
 
-	if (!ct->ext)
+	if (!ct->ext) {
 		memset(new->offset, 0, sizeof(new->offset));
+		new->gen_id = atomic_read(&nf_conntrack_ext_genid);
+	}
 
 	new->offset[id] = newoff;
 	new->len = newlen;
@@ -127,3 +131,29 @@ void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
 	return (void *)new + newoff;
 }
 EXPORT_SYMBOL(nf_ct_ext_add);
+
+/* Use nf_ct_ext_find wrapper. This is only useful for unconfirmed entries. */
+void *__nf_ct_ext_find(const struct nf_ct_ext *ext, u8 id)
+{
+	unsigned int gen_id = atomic_read(&nf_conntrack_ext_genid);
+	unsigned int this_id = READ_ONCE(ext->gen_id);
+
+	if (!__nf_ct_ext_exist(ext, id))
+		return NULL;
+
+	if (this_id == 0 || ext->gen_id == gen_id)
+		return (void *)ext + ext->offset[id];
+
+	return NULL;
+}
+EXPORT_SYMBOL(__nf_ct_ext_find);
+
+void nf_ct_ext_bump_genid(void)
+{
+	unsigned int value = atomic_inc_return(&nf_conntrack_ext_genid);
+
+	if (value == UINT_MAX)
+		atomic_set(&nf_conntrack_ext_genid, 1);
+
+	msleep(HZ);
+}