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

From: Maciej S. Szmigiero
Date: Thu Sep 03 2015 - 15:38:45 EST

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() ->

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.

Signed-off-by: Maciej Szmigiero <mail@xxxxxxxxxxxxxxxxxxxxx>
drivers/net/ethernet/freescale/fec_main.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 91925e3..6cc3340 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1816,11 +1816,13 @@ static int fec_enet_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
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;
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