[PATCH] net: phy: micrel: KSZ9031: fix crash when statistic requested

[Grygorii Strashko]

Now the command:
        ethtool --phy-statistics eth0
will cause system crash with meassage "Unable to handle kernel NULL pointer
dereference at virtual address 00000010" from:

 (kszphy_get_stats) from [<c069f1d8>] (ethtool_get_phy_stats+0xd8/0x210)
 (ethtool_get_phy_stats) from [<c06a0738>] (dev_ethtool+0x5b8/0x228c)
 (dev_ethtool) from [<c06b5484>] (dev_ioctl+0x3fc/0x964)
 (dev_ioctl) from [<c0679f7c>] (sock_ioctl+0x170/0x2c0)
 (sock_ioctl) from [<c02419d4>] (do_vfs_ioctl+0xa8/0x95c)
 (do_vfs_ioctl) from [<c02422c4>] (SyS_ioctl+0x3c/0x64)
 (SyS_ioctl) from [<c0107d60>] (ret_fast_syscall+0x0/0x44)

The reason: phy_driver structure for KSZ9031 phy has no .probe() callback
defined. As result, struct phy_device *phydev->priv pointer will not be
initializes (null).

Fix it by adding additional checks for !phydev->priv in
kszphy_get_stats(), kszphy_get_strings() and kszphy_get_sset_count()

Fixes: 2b2427d06426 ("phy: micrel: Add ethtool statistics counters")
Signed-off-by: Grygorii Strashko <grygorii.stras...@ti.com>
---
 drivers/net/phy/micrel.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 6742070..8dbc1be 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -574,7 +574,6 @@ static int ksz9031_config_init(struct phy_device *phydev)
                                MII_KSZ9031RN_TX_DATA_PAD_SKEW, 4,
                                tx_data_skews, 4);
        }
-
        return ksz9031_center_flp_timing(phydev);
 }
 
@@ -654,6 +653,9 @@ ksz9021_wr_mmd_phyreg(struct phy_device *phydev, int ptrad, 
int devnum,
 
 static int kszphy_get_sset_count(struct phy_device *phydev)
 {
+       if (!phydev->priv)
+               return -EOPNOTSUPP;
+
        return ARRAY_SIZE(kszphy_hw_stats);
 }
 
@@ -661,6 +663,9 @@ static void kszphy_get_strings(struct phy_device *phydev, 
u8 *data)
 {
        int i;
 
+       if (!phydev->priv)
+               return;
+
        for (i = 0; i < ARRAY_SIZE(kszphy_hw_stats); i++) {
                memcpy(data + i * ETH_GSTRING_LEN,
                       kszphy_hw_stats[i].string, ETH_GSTRING_LEN);
@@ -694,6 +699,9 @@ static void kszphy_get_stats(struct phy_device *phydev,
 {
        int i;
 
+       if (!phydev->priv)
+               return;
+
        for (i = 0; i < ARRAY_SIZE(kszphy_hw_stats); i++)
                data[i] = kszphy_get_stat(phydev, i);
 }
-- 
2.10.1