From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit 70f360dd7042cb843635ece9d28335a4addff9eb ]
This field can be read locklessly.
Fixes: 1536e2857bd3 ("tcp: Add a TCP_FASTOPEN socket option to get a max backlog on its listner")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230719212857.3943972-12-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/linux/tcp.h | 2 +-
net/ipv4/tcp.c | 2 +-
net/ipv4/tcp_fastopen.c | 6 ++++--
3 files changed, 6 insertions(+), 4 deletions(-)
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -425,7 +425,7 @@ static inline void fastopen_queue_tune(s
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 = min_t(unsigned int, backlog, somaxconn);
+ WRITE_ONCE(queue->fastopenq.max_qlen, min_t(unsigned int, backlog, somaxconn));
}
static inline void tcp_move_syn(struct tcp_sock *tp,
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3193,7 +3193,7 @@ static int do_tcp_getsockopt(struct sock
break;
case TCP_FASTOPEN:
- val = icsk->icsk_accept_queue.fastopenq.max_qlen;
+ val = READ_ONCE(icsk->icsk_accept_queue.fastopenq.max_qlen);
break;
case TCP_FASTOPEN_CONNECT:
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -239,6 +239,7 @@ static struct sock *tcp_fastopen_create_
static bool tcp_fastopen_queue_check(struct sock *sk)
{
struct fastopen_queue *fastopenq;
+ int max_qlen;
/* Make sure the listener has enabled fastopen, and we don't
* exceed the max # of pending TFO requests allowed before trying
@@ -251,10 +252,11 @@ static bool tcp_fastopen_queue_check(str
* temporarily vs a server not supporting Fast Open at all.
*/
fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
- if (fastopenq->max_qlen == 0)
+ max_qlen = READ_ONCE(fastopenq->max_qlen);
+ if (max_qlen == 0)
return false;
- if (fastopenq->qlen >= fastopenq->max_qlen) {
+ if (fastopenq->qlen >= max_qlen) {
struct request_sock *req1;
spin_lock(&fastopenq->lock);
req1 = fastopenq->rskq_rst_head;
