From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Wed, 20 Jul 2022 16:50:20 +0000 (-0700)
Subject: tcp: Fix a data-race around sysctl_tcp_limit_output_bytes.
X-Git-Tag: v5.4.209~23
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dfdc635d55f92db58a63dc52d0f5d6ee651c73ec;p=thirdparty%2Fkernel%2Fstable.git

tcp: Fix a data-race around sysctl_tcp_limit_output_bytes.

commit 9fb90193fbd66b4c5409ef729fd081861f8b6351 upstream.

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

Fixes: 46d3ceabd8d9 ("tcp: TCP Small Queues")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 97f29ece38000..99e0774229757 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2276,7 +2276,7 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
 		      sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift));
 	if (sk->sk_pacing_status == SK_PACING_NONE)
 		limit = min_t(unsigned long, limit,
-			      sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
+			      READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes));
 	limit <<= factor;
 
 	if (static_branch_unlikely(&tcp_tx_delay_enabled) &&