[PATCH 5.19 075/158] net: Fix data-races around sysctl_max_skb_frags.

Greg Kroah-Hartman
2022-08-29T11:27:27Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ 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>
---
net/ipv4/tcp.c | 4 ++--
net/mptcp/protocol.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)

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 @@ static struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags,

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 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)

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;
}
--
2.35.1