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 <rl@hellgate.ch>
---

Bug verified. Patch only compile-tested.

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

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 <rl@hellgate.ch>
Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>

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

Ben.

> ---
> 
> 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;
>

2011/3/17 Roger Luethi <rl@hellgate.ch>:
> __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 <rl@hellgate.ch>
> ---
>
> 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;
>

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
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From: Ben Hutchings <bhutchings@solarflare.com>
Date: Thu, 17 Mar 2011 16:52:13 +0000

> 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 <rl@hellgate.ch>
> Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>

Applied.
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