Commit 30c57f07 authored Apr 03, 2017 by Sekhar Nori Committed by David S. Miller Apr 04, 2017

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>

parent 249ee819

drivers/net/ethernet/ti/cpsw.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -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);