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 f264ea15e081b38d5670e02f1e61129304cce2bc..f2455a68d2315c1abb6571bd0971f879f43819e7 100644 (file)
--- 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);