[PATCH v3] net: sun: sungem: rix a possible null dereference

The function gem_begin_auto_negotiation dereference
the pointer ep before testing if it's null. This
patch add a check on ep before dereferencing it.

Fixes: 92552fdda557 ("net: sun: sungem: use new api
ethtool_{get|set}_link_ksettings")

Reported-by: Dan Carpenter <redacted>
Signed-off-by: Philippe Reynes <redacted>
---
Changelog:
v3:
- fix the sha1-id in the tag Fixes (thanks David Miller)
v2:
- use Fixes tag (thanks Sergei Shtylyov)

 drivers/net/ethernet/sun/sungem.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/sun/sungem.c b/drivers/net/ethernet/sun/sungem.c
index dbfca04..fa607d0 100644
--- a/drivers/net/ethernet/sun/sungem.c
+++ b/drivers/net/ethernet/sun/sungem.c

@@ -1259,8 +1259,9 @@ static void gem_begin_auto_negotiation(struct gem *gp,
 	int duplex;
 	u32 advertising;
 
-	ethtool_convert_link_mode_to_legacy_u32(&advertising,
-						ep->link_modes.advertising);
+	if (ep)
+		ethtool_convert_link_mode_to_legacy_u32(
+			&advertising, ep->link_modes.advertising);
 
 	if (gp->phy_type != phy_mii_mdio0 &&
      	    gp->phy_type != phy_mii_mdio1)

-- 
1.7.4.4