[PATCH 5.10 052/105] tcp: Fix a data-race around sysctl_tcp_notsent_lowat.

Greg Kroah-Hartman
2022-07-27T16:56:57Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 55be873695ed8912eb77ff46d1d1cadf028bd0f3 ]

While reading sysctl_tcp_notsent_lowat, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: c9bee3b7fdec ("tcp: TCP_NOTSENT_LOWAT socket option")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/tcp.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index da75513a77d4..aa46f4016245 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1973,7 +1973,7 @@ 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 ?: net->ipv4.sysctl_tcp_notsent_lowat;
+ return tp->notsent_lowat ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
}

/* @wake is one when sk_stream_write_space() calls us.
--
2.35.1