netdev - Re:Re: [PATCH] wifi: plfxlc: fix potential NULL pointer dereference in plfxlc_usb_wreq

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Date:   Fri, 3 Feb 2023 16:48:10 +0800 (CST)
From:   王征 <zyytlz.wz@....com>
To:     "Christophe JAILLET" <christophe.jaillet@...adoo.fr>
Cc:     srini.raju@...elifi.com, kvalo@...nel.org, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re:Re: [PATCH] wifi: plfxlc: fix potential NULL pointer dereference
 in plfxlc_usb_wreq_async()

















At 2023-02-03 13:25:45, "Christophe JAILLET" <christophe.jaillet@...adoo.fr> wrote:
>Le 03/02/2023 à 05:16, Zheng Wang a écrit :
>> Although the usb_alloc_urb uses GFP_ATOMIC, tring to make sure the memory
>>   allocated not to be NULL. But in some low-memory situation, it's still
>>   possible to return NULL. It'll pass urb as argument in
>>   usb_fill_bulk_urb, which will finally lead to a NULL pointer dereference.
>> 
>> Fix it by adding additional check.
>> 
>> Note that, as a bug found by static analysis, it can be a false
>> positive or hard to trigger.
>> 
>> Fixes: 68d57a07bfe5 ("wireless: add plfxlc driver for pureLiFi X, XL, XC devices")
>> 
>> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
>> ---
>>   drivers/net/wireless/purelifi/plfxlc/usb.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>> 
>> diff --git a/drivers/net/wireless/purelifi/plfxlc/usb.c b/drivers/net/wireless/purelifi/plfxlc/usb.c
>> index 76d0a778636a..ac149aa64908 100644
>> --- a/drivers/net/wireless/purelifi/plfxlc/usb.c
>> +++ b/drivers/net/wireless/purelifi/plfxlc/usb.c
>> @@ -496,10 +496,17 @@ int plfxlc_usb_wreq_async(struct plfxlc_usb *usb, const u8 *buffer,
>>   	struct urb *urb = usb_alloc_urb(0, GFP_ATOMIC);
>>   	int r;
>>   
>> +	if (!urb) {
>> +		r = -ENOMEM;
>> +		kfree(urb);
>
>Hi,
>why kfree() in such a case?


Hello CJ,


Thanks for pointing that out. Kfree is unnecessary in such case, we can just return.


Regards,
Zheng Wang

>
>> +		goto out;
>> +	}
>>   	usb_fill_bulk_urb(urb, udev, usb_sndbulkpipe(udev, EP_DATA_OUT),
>>   			  (void *)buffer, buffer_len, complete_fn, context);
>>   
>>   	r = usb_submit_urb(urb, GFP_ATOMIC);
>> +
>> +out:
>>   	if (r)
>>   		dev_err(&udev->dev, "Async write submit failed (%d)\n", r);
>>