From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit 1aeb87bc1440c5447a7fa2d6e3c2cca52cbd206b ]
tp->notsent_lowat can be read locklessly from do_tcp_getsockopt()
and tcp_poll().
Fixes: c9bee3b7fdec ("tcp: TCP_NOTSENT_LOWAT socket option")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230719212857.3943972-10-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/net/tcp.h | 6 +++++-
net/ipv4/tcp.c | 4 ++--
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4f97c0e2d5f34..b1a9e6b1a1533 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1887,7 +1887,11 @@ void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
{
struct net *net = sock_net((struct sock *)tp);
- return tp->notsent_lowat ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
+ u32 val;
+
+ val = READ_ONCE(tp->notsent_lowat);
+
+ return val ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
}
static inline bool tcp_stream_memory_free(const struct sock *sk)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 98811b5f2451a..bcc2a3490323b 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2810,7 +2810,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
err = tcp_repair_set_window(tp, optval, optlen);
break;
case TCP_NOTSENT_LOWAT:
- tp->notsent_lowat = val;
+ WRITE_ONCE(tp->notsent_lowat, val);
sk->sk_write_space(sk);
break;
default:
@@ -3204,7 +3204,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
val = tcp_time_stamp_raw() + tp->tsoffset;
break;
case TCP_NOTSENT_LOWAT:
- val = tp->notsent_lowat;
+ val = READ_ONCE(tp->notsent_lowat);
break;
case TCP_SAVE_SYN:
val = tp->save_syn;
--
2.39.2
