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 fa76ce7328b ("inet: get rid of central tcp/dccp listener
timer"), we were holding listener lock so lockdep was happy.
Fixes: fa76ce7328b ("inet: get rid of central tcp/dccp listener timer")
Signed-off-by: Eric DUmazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 1847408..5b7fad4 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -601,15 +601,14 @@
struct request_sock *req,
unsigned int mss, struct sk_buff *skb,
struct tcp_out_options *opts,
- struct tcp_md5sig_key **md5,
+ const struct tcp_md5sig_key *md5,
struct tcp_fastopen_cookie *foc)
{
struct inet_request_sock *ireq = inet_rsk(req);
unsigned int remaining = MAX_TCP_OPTION_SPACE;
#ifdef CONFIG_TCP_MD5SIG
- *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
- if (*md5) {
+ if (md5) {
opts->options |= OPTION_MD5;
remaining -= TCPOLEN_MD5SIG_ALIGNED;
@@ -620,8 +619,6 @@
*/
ireq->tstamp_ok &= !ireq->sack_ok;
}
-#else
- *md5 = NULL;
#endif
/* We always send an MSS option. */
@@ -2913,7 +2910,7 @@
struct tcp_sock *tp = tcp_sk(sk);
struct tcphdr *th;
struct sk_buff *skb;
- struct tcp_md5sig_key *md5;
+ struct tcp_md5sig_key *md5 = NULL;
int tcp_header_size;
int mss;
@@ -2938,7 +2935,12 @@
else
#endif
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);
skb_push(skb, tcp_header_size);
@@ -2969,10 +2971,10 @@
#ifdef CONFIG_TCP_MD5SIG
/* 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,
md5, NULL, req, skb);
- }
+ rcu_read_unlock();
#endif
return skb;