[PATCH AUTOSEL 4.19 37/59] net/smc: receive pending data after RCV_SHUTDOWN

Sasha Levin
2019-10-26T13:20:43Z

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