[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

On Thu, 2011-03-17 at 17:37 +0100, Roger Luethi wrote:

__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>

Reviewed-by: Ben Hutchings <redacted>

Michał, was this just an oversight or is there some reason why we
shouldn't check set_sg immediately?

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

2011/3/17 Roger Luethi [off-list ref]:

Yes. __ethtool_set_sg() is the only function that was already there
before my unification series and I did tests only on drivers which had
set_sg() defined. :-/

This should go into 2.6.39 as a bugfix (adding Cc: DaveM).

Best Regards,
Michał Mirosław

From: Ben Hutchings <redacted>
Date: Thu, 17 Mar 2011 16:52:13 +0000

On Thu, 2011-03-17 at 17:37 +0100, Roger Luethi wrote:

quoted

__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>

Reviewed-by: Ben Hutchings <redacted>

Applied.