[PATCH] ethtool: __ethtool_set_sg: check for function pointer before using it

__ethtool_set_sg does not check if dev->ethtool_ops->set_sg is defined
which can result in a NULL pointer dereference when ethtool is used to
change SG settings for drivers without SG support.

Signed-off-by: Roger Luethi <redacted>
---

Bug verified. Patch only compile-tested.

 net/core/ethtool.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index c1a71bb..a1086fb 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c

@@ -1457,6 +1457,9 @@ static int __ethtool_set_sg(struct net_device *dev, u32 data)
 {
 	int err;
 
+	if (!dev->ethtool_ops->set_sg)
+		return -EOPNOTSUPP;
+
 	if (data && !(dev->features & NETIF_F_ALL_CSUM))
 		return -EINVAL;
 

-- 
1.7.3.4