Patch "net: fec: normalize return value of pm_runtime_get_sync() in MDIO write" has been added to the 4.2-stable tree

This is a note to let you know that I've just added the patch titled

net: fec: normalize return value of pm_runtime_get_sync() in MDIO write

to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-fec-normalize-return-value-of-pm_runtime_get_sync-in-mdio-write.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Maciej S. Szmigiero" <[email protected]>
Date: Thu, 3 Sep 2015 21:38:30 +0200
Subject: net: fec: normalize return value of pm_runtime_get_sync() in MDIO write

From: "Maciej S. Szmigiero" <[email protected]>

[ Upstream commit 42ea4457aea7aaeddf0c0b06724f297608f5e9d2 ]

If fec MDIO write method succeeds its return value comes from call to pm_runtime_get_sync().
But pm_runtime_get_sync() can also return 1.

In case of Micrel KSZ9031 PHY this value will then
be returned along the call chain of phy_write() -> ksz9031_extended_write() -> ksz9031_center_flp_timing() -> ksz9031_config_init() -> phy_init_hw() -> phy_attach_direct() -> phy_connect_direct().

Then phy_connect() will cast it into a pointer using ERR_PTR(), which then fec_enet_mii_probe() will try to dereference resulting in an oops.

Fix it by normalizing return value of pm_runtime_get_sync() to be zero if positive in MDIO write method.

---
 drivers/net/ethernet/freescale/fec_main.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -1811,11 +1811,13 @@ static int fec_enet_mdio_write(struct mi
 	struct fec_enet_private *fep = bus->priv;
 	struct device *dev = &fep->pdev->dev;
 	unsigned long time_left;
-	int ret = 0;
+	int ret;
 
 	ret = pm_runtime_get_sync(dev);
 	if (ret < 0)
 		return ret;
+	else
+		ret = 0;
 
 	fep->mii_timeout = 0;
 	reinit_completion(&fep->mdio_done);

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/net-fec-normalize-return-value-of-pm_runtime_get_sync-in-mdio-write.patch