netdev - Re: [PATCH 1/1] net: thunderx: avoid null pointer dereference

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Date:	Tue, 17 May 2016 23:37:11 +0200
From:	Heinrich Schuchardt <xypron.glpk@....de>
To:	David Daney <ddaney@...iumnetworks.com>
Cc:	Sunil Goutham <sgoutham@...ium.com>,
	Robert Richter <rric@...nel.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] net: thunderx: avoid null pointer dereference



On 05/17/2016 10:21 PM, David Daney wrote:
> On 05/17/2016 12:40 PM, Heinrich Schuchardt wrote:
>> In function bgx_lmac_handler only use a member of
>> lmac after checking it is not null.
>>
> 
> Were you seeing and actual OOPs, or is this only a theoretical problem
> flagged by some sort of static code checker?

Cppcheck identified the code inconsistency.

If the struct netdev * parameter cannot be NULL, you could eliminate the
check.

Other drivers do no have check against a NULL parameter in the
adjust_link handler function (e.g. bgmac_adjust_link,
pxa168_eth_adjust_link).

Best regards

Heinrich

> 
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
> 
> In any event, it seems sane to make this change, so:
> 
> Acked-by: David Daney <david.daney@...ium.com>
> 
> 
>> ---
>>   drivers/net/ethernet/cavium/thunder/thunder_bgx.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
>> b/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
>> index d20539a..3ed2198 100644
>> --- a/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
>> +++ b/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
>> @@ -274,12 +274,14 @@ static void bgx_sgmii_change_link_state(struct
>> lmac *lmac)
>>   static void bgx_lmac_handler(struct net_device *netdev)
>>   {
>>       struct lmac *lmac = container_of(netdev, struct lmac, netdev);
>> -    struct phy_device *phydev = lmac->phydev;
>> +    struct phy_device *phydev;
>>       int link_changed = 0;
>>
>>       if (!lmac)
>>           return;
>>
>> +    phydev = lmac->phydev;
>> +
>>       if (!phydev->link && lmac->last_link)
>>           link_changed = -1;
>>
>>
> 
>