From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Tue, 23 Aug 2022 17:46:54 +0000 (-0700)
Subject: net: Fix data-races around sysctl_max_skb_frags.
X-Git-Tag: v5.19.6~84
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c34e06f05ab7163a461e550a70e81a7256079789;p=thirdparty%2Fkernel%2Fstable.git

net: Fix data-races around sysctl_max_skb_frags.

[ Upstream commit 657b991afb89d25fe6c4783b1b75a8ad4563670d ]

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

Fixes: 5f74f82ea34c ("net:Add sysctl_max_skb_frags")
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>
---

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 3ae2ea0488838..3d446773ff2a5 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1000,7 +1000,7 @@ new_segment:
 
 	i = skb_shinfo(skb)->nr_frags;
 	can_coalesce = skb_can_coalesce(skb, i, page, offset);
-	if (!can_coalesce && i >= sysctl_max_skb_frags) {
+	if (!can_coalesce && i >= READ_ONCE(sysctl_max_skb_frags)) {
 		tcp_mark_push(tp, skb);
 		goto new_segment;
 	}
@@ -1348,7 +1348,7 @@ new_segment:
 
 			if (!skb_can_coalesce(skb, i, pfrag->page,
 					      pfrag->offset)) {
-				if (i >= sysctl_max_skb_frags) {
+				if (i >= READ_ONCE(sysctl_max_skb_frags)) {
 					tcp_mark_push(tp, skb);
 					goto new_segment;
 				}
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 3d90fa9653ef3..513f571a082ba 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1299,7 +1299,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 
 		i = skb_shinfo(skb)->nr_frags;
 		can_coalesce = skb_can_coalesce(skb, i, dfrag->page, offset);
-		if (!can_coalesce && i >= sysctl_max_skb_frags) {
+		if (!can_coalesce && i >= READ_ONCE(sysctl_max_skb_frags)) {
 			tcp_mark_push(tcp_sk(ssk), skb);
 			goto alloc_skb;
 		}