tcp: fastopen: limit max_qlen

Eric Dumazet · davem330 · commit dbf650b67bb4 · 2015-10-22T06:22:13.000-07:00
Allowing an application to set whatever limit for the list of recently RST fastopen sessions [1] is not wise, as it open ways to deplete kernel memory. Cap the user provided limit by somaxconn sysctl, like listen() backlog. [1] https://tools.ietf.org/html/rfc7413#section-5.1 Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
@@ -392,8 +392,9 @@ static inline bool tcp_passive_fastopen(const struct sock *sk)
 static inline void fastopen_queue_tune(struct sock *sk, int backlog)
 {
 	struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
+	int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
 
-	queue->fastopenq.max_qlen = backlog;
+	queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
 }
 
 static inline void tcp_saved_syn_free(struct tcp_sock *tp)

Original file line number	Diff line number	Diff line change
`@@ -392,8 +392,9 @@ static inline bool tcp_passive_fastopen(const struct sock *sk)`
`392`	`392`	`static inline void fastopen_queue_tune(struct sock *sk, int backlog)`
`393`	`393`	`{`
`394`	`394`	`struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;`
	`395`	`+ int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);`
`395`	`396`
`396`		`- queue->fastopenq.max_qlen = backlog;`
	`397`	`+ queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);`
`397`	`398`	`}`
`398`	`399`
`399`	`400`	`static inline void tcp_saved_syn_free(struct tcp_sock *tp)`