mptcp: Safely store sequence number when sending data

The MPTCP socket's write_seq member can be read without the msk lock
held, so use WRITE_ONCE() to store it.

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 f2455a6..687f0be 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -793,7 +793,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 out:
        if (!retransmission)
                pfrag->offset += frag_truesize;
-       *write_seq += ret;
+       WRITE_ONCE(*write_seq, *write_seq + ret);
        mptcp_subflow_ctx(ssk)->rel_write_seq += ret;
 
        return ret;