net: ethernet: ti: cpsw: fix race condition during open()

TI's cpsw driver handles both OF and non-OF case for phy
connect. Unfortunately of_phy_connect() returns NULL on
error while phy_connect() returns ERR_PTR().

To handle this, cpsw_slave_open() overrides the return value
from phy_connect() to make it NULL or error.

This leaves a small window, where cpsw_adjust_link() may be
invoked for a slave while slave->phy pointer is temporarily
set to -ENODEV (or some other error) before it is finally set
to NULL.

_cpsw_adjust_link() only handles the NULL case, and an oops
results when ERR_PTR() is seen by it.

Note that cpsw_adjust_link() checks PHY status for each
slave whenever it is invoked. It can so happen that even
though phy_connect() for a given slave returns error,
_cpsw_adjust_link() is still called for that slave because
the link status of another slave changed.

Fix this by using a temporary pointer to store return value
of {of_}phy_connect() and do a one-time write to slave->phy.

Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reported-by: Yan Liu <yan-liu@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
index 58cdc066ef2c..fa674a8bda0c 100644
--- a/drivers/net/ethernet/ti/cpsw.c
+++ b/drivers/net/ethernet/ti/cpsw.c
@@ -1267,6 +1267,7 @@ static void soft_reset_slave(struct cpsw_slave *slave)
 static void cpsw_slave_open(struct cpsw_slave *slave, struct cpsw_priv *priv)
 {
         u32 slave_port;
+        struct phy_device *phy;
         struct cpsw_common *cpsw = priv->cpsw;
 
         soft_reset_slave(slave);
@@ -1300,27 +1301,28 @@ static void cpsw_slave_open(struct cpsw_slave *slave, struct cpsw_priv *priv)
                                    1 << slave_port, 0, 0, ALE_MCAST_FWD_2);
 
         if (slave->data->phy_node) {
-                slave->phy = of_phy_connect(priv->ndev, slave->data->phy_node,
+                phy = of_phy_connect(priv->ndev, slave->data->phy_node,
                                  &cpsw_adjust_link, 0, slave->data->phy_if);
-                if (!slave->phy) {
+                if (!phy) {
                         dev_err(priv->dev, "phy \"%s\" not found on slave %d\n",
                                 slave->data->phy_node->full_name,
                                 slave->slave_num);
                         return;
                 }
         } else {
-                slave->phy = phy_connect(priv->ndev, slave->data->phy_id,
+                phy = phy_connect(priv->ndev, slave->data->phy_id,
                                  &cpsw_adjust_link, slave->data->phy_if);
-                if (IS_ERR(slave->phy)) {
+                if (IS_ERR(phy)) {
                         dev_err(priv->dev,
                                 "phy \"%s\" not found on slave %d, err %ld\n",
                                 slave->data->phy_id, slave->slave_num,
-                                PTR_ERR(slave->phy));
-                        slave->phy = NULL;
+                                PTR_ERR(phy));
                         return;
                 }
         }
 
+        slave->phy = phy;
+
         phy_attached_info(slave->phy);
 
         phy_start(slave->phy);