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Commit 80f03e27 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: md5: fix rcu lockdep splat 



While timer handler effectively runs a rcu read locked section,
there is no explicit rcu_read_lock()/rcu_read_unlock() annotations
and lockdep can be confused here :

net/ipv4/tcp_ipv4.c-906-        /* caller either holds rcu_read_lock() or socket lock */
net/ipv4/tcp_ipv4.c:907:        md5sig = rcu_dereference_check(tp->md5sig_info,
net/ipv4/tcp_ipv4.c-908-                                       sock_owned_by_user(sk) ||
net/ipv4/tcp_ipv4.c-909-                                       lockdep_is_held(&sk->sk_lock.slock));

Let's explicitely acquire rcu_read_lock() in tcp_make_synack()

Before commit fa76ce73 ("inet: get rid of central tcp/dccp listener
timer"), we were holding listener lock so lockdep was happy.

Fixes: fa76ce73 ("inet: get rid of central tcp/dccp listener timer")
Signed-off-by: default avatarEric DUmazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9ead3527

net/ipv4/tcp_output.c

+11 −9
Original line number Original line Diff line number Diff line
@@ -601,15 +601,14 @@ static unsigned int tcp_synack_options(struct sock *sk, 
				   struct request_sock *req,

				   struct request_sock *req,

				   unsigned int mss, struct sk_buff *skb,

				   unsigned int mss, struct sk_buff *skb,

				   struct tcp_out_options *opts,

				   struct tcp_out_options *opts,

				   struct tcp_md5sig_key **md5,

				   const struct tcp_md5sig_key *md5,

				   struct tcp_fastopen_cookie *foc)

				   struct tcp_fastopen_cookie *foc)

{

{

	struct inet_request_sock *ireq = inet_rsk(req);

	struct inet_request_sock *ireq = inet_rsk(req);

	unsigned int remaining = MAX_TCP_OPTION_SPACE;

	unsigned int remaining = MAX_TCP_OPTION_SPACE;





#ifdef CONFIG_TCP_MD5SIG

#ifdef CONFIG_TCP_MD5SIG

	*md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);

	if (md5) {

	if (*md5) {

		opts->options |= OPTION_MD5;

		opts->options |= OPTION_MD5;

		remaining -= TCPOLEN_MD5SIG_ALIGNED;

		remaining -= TCPOLEN_MD5SIG_ALIGNED;
@@ -620,8 +619,6 @@ static unsigned int tcp_synack_options(struct sock *sk, 
		 */

		 */

		ireq->tstamp_ok &= !ireq->sack_ok;

		ireq->tstamp_ok &= !ireq->sack_ok;

	}

	}

#else

	*md5 = NULL;

#endif

#endif





	/* We always send an MSS option. */

	/* We always send an MSS option. */
@@ -2913,7 +2910,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, 
	struct tcp_sock *tp = tcp_sk(sk);

	struct tcp_sock *tp = tcp_sk(sk);

	struct tcphdr *th;

	struct tcphdr *th;

	struct sk_buff *skb;

	struct sk_buff *skb;

	struct tcp_md5sig_key *md5;

	struct tcp_md5sig_key *md5 = NULL;

	int tcp_header_size;

	int tcp_header_size;

	int mss;

	int mss;
@@ -2938,7 +2935,12 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, 
	else

	else

#endif

#endif

	skb_mstamp_get(&skb->skb_mstamp);

	skb_mstamp_get(&skb->skb_mstamp);

	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5,



#ifdef CONFIG_TCP_MD5SIG

	rcu_read_lock();

	md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);

#endif

	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,

					     foc) + sizeof(*th);

					     foc) + sizeof(*th);





	skb_push(skb, tcp_header_size);

	skb_push(skb, tcp_header_size);
@@ -2969,10 +2971,10 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, 




#ifdef CONFIG_TCP_MD5SIG

#ifdef CONFIG_TCP_MD5SIG

	/* Okay, we have all we need - do the md5 hash if needed */

	/* Okay, we have all we need - do the md5 hash if needed */

	if (md5) {

	if (md5)

		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,

		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,

					       md5, NULL, req, skb);

					       md5, NULL, req, skb);

	}

	rcu_read_unlock();

#endif

#endif





	return skb;

	return skb;