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    Subject[PATCH 4.19 603/639] net/smc: receive pending data after RCV_SHUTDOWN
    Date
    From: Karsten Graul <kgraul@linux.ibm.com>

    [ Upstream commit 107529e31a87acd475ff6a0f82745821b8f70fec ]

    smc_rx_recvmsg() first checks if data is available, and then if
    RCV_SHUTDOWN is set. There is a race when smc_cdc_msg_recv_action() runs
    in between these 2 checks, receives data and sets RCV_SHUTDOWN.
    In that case smc_rx_recvmsg() would return from receive without to
    process the available data.
    Fix that with a final check for data available if RCV_SHUTDOWN is set.
    Move the check for data into a function and call it twice.
    And use the existing helper smc_rx_data_available().

    Fixes: 952310ccf2d8 ("smc: receive data from RMBE")
    Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
    Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
    Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/smc/smc_rx.c | 25 ++++++++++++++++++++-----
    1 file changed, 20 insertions(+), 5 deletions(-)

    diff --git a/net/smc/smc_rx.c b/net/smc/smc_rx.c
    index 1ee5fdbf8284e..36340912df48a 100644
    --- a/net/smc/smc_rx.c
    +++ b/net/smc/smc_rx.c
    @@ -262,6 +262,18 @@ static int smc_rx_recv_urg(struct smc_sock *smc, struct msghdr *msg, int len,
    return -EAGAIN;
    }

    +static bool smc_rx_recvmsg_data_available(struct smc_sock *smc)
    +{
    + struct smc_connection *conn = &smc->conn;
    +
    + if (smc_rx_data_available(conn))
    + return true;
    + else if (conn->urg_state == SMC_URG_VALID)
    + /* we received a single urgent Byte - skip */
    + smc_rx_update_cons(smc, 0);
    + return false;
    +}
    +
    /* smc_rx_recvmsg - receive data from RMBE
    * @msg: copy data to receive buffer
    * @pipe: copy data to pipe if set - indicates splice() call
    @@ -303,15 +315,18 @@ int smc_rx_recvmsg(struct smc_sock *smc, struct msghdr *msg,
    if (read_done >= target || (pipe && read_done))
    break;

    - if (atomic_read(&conn->bytes_to_rcv))
    + if (smc_rx_recvmsg_data_available(smc))
    goto copy;
    - else if (conn->urg_state == SMC_URG_VALID)
    - /* we received a single urgent Byte - skip */
    - smc_rx_update_cons(smc, 0);

    if (sk->sk_shutdown & RCV_SHUTDOWN ||
    - conn->local_tx_ctrl.conn_state_flags.peer_conn_abort)
    + conn->local_tx_ctrl.conn_state_flags.peer_conn_abort) {
    + /* smc_cdc_msg_recv_action() could have run after
    + * above smc_rx_recvmsg_data_available()
    + */
    + if (smc_rx_recvmsg_data_available(smc))
    + goto copy;
    break;
    + }

    if (read_done) {
    if (sk->sk_err ||
    --
    2.20.1


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