netdev - Re: [PATCH -next] mISDN: hfcsusb: Fix potential NULL pointer dereference

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Date:   Thu, 31 Jan 2019 09:25:58 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     yuehaibing@...wei.com
Cc:     isdn@...ux-pingi.de, gustavo@...eddedor.com, bigeasy@...utronix.de,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH -next] mISDN: hfcsusb: Fix potential NULL pointer
 dereference

From: YueHaibing <yuehaibing@...wei.com>
Date: Thu, 31 Jan 2019 17:41:46 +0800

> On 2019/1/31 2:10, David Miller wrote:
>> From: YueHaibing <yuehaibing@...wei.com>
>> Date: Wed, 30 Jan 2019 18:19:02 +0800
>> 
>>> There is a potential NULL pointer dereference in case
>>> kzalloc() fails and returns NULL.
>>>
>>> Fixes: 69f52adb2d53 ("mISDN: Add HFC USB driver")
>>> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
>>> ---
>>>  drivers/isdn/hardware/mISDN/hfcsusb.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/isdn/hardware/mISDN/hfcsusb.c b/drivers/isdn/hardware/mISDN/hfcsusb.c
>>> index 124ff53..5660d5a 100644
>>> --- a/drivers/isdn/hardware/mISDN/hfcsusb.c
>>> +++ b/drivers/isdn/hardware/mISDN/hfcsusb.c
>>> @@ -263,6 +263,8 @@ hfcsusb_ph_info(struct hfcsusb *hw)
>>>  	int i;
>>>  
>>>  	phi = kzalloc(struct_size(phi, bch, dch->dev.nrbchan), GFP_ATOMIC);
>>> +	if (!phi)
>>> +		return;
>> 
>> If we fail with an error and do not perform the operation we were requested to
>> make, we must return an error to the caller, and the caller must do something
>> reasonable with that error (perhaps return it to it's caller) and so on and
>> so forth.
> 
> 
> hfcsusb_ph_info alloced the 'phi'，then use it _alloc_mISDN_skb in _queue_data.
> while _alloc_mISDN_skb fails, it also just return without err handling,then kfree(phi).
> It seems that all the caller of hfcsusb_ph_info doesn't care the return value.

And that's a bug!