From: Mat Martineau <mathew.j.martineau@linux.intel.com>
Date: Tue, 28 Jul 2020 22:12:09 +0000 (-0700)
Subject: mptcp: Safely read sequence number when lock isn't held
X-Git-Tag: x86-urgent-2020-08-15~21^2~110^2~1
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=c75293925f24630326abdf79751d980ec3878f65;p=users%2Fdwmw2%2Flinux.git

mptcp: Safely read sequence number when lock isn't held

The MPTCP socket's write_seq member should be read with READ_ONCE() when
the msk lock is not held.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index f264ea15e081b..f2455a68d2315 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1269,7 +1269,7 @@ static void mptcp_retransmit_handler(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
 
-	if (atomic64_read(&msk->snd_una) == msk->write_seq) {
+	if (atomic64_read(&msk->snd_una) == READ_ONCE(msk->write_seq)) {
 		mptcp_stop_timer(sk);
 	} else {
 		set_bit(MPTCP_WORK_RTX, &msk->flags);