Re: [PATCH 2/2] Fix a NULL-ptr-deref bug in ath10k_usb_alloc_urb_from_pipe

[Hui Peng]

On 8/31/19 5:31 PM, Guenter Roeck wrote:
> Hi,
>
> On Sat, Aug 03, 2019 at 08:31:01PM -0400, Hui Peng wrote:
>> The `ar_usb` field of `ath10k_usb_pipe_usb_pipe` objects
>> are initialized to point to the containing `ath10k_usb` object
>> according to endpoint descriptors read from the device side, as shown
>> below in `ath10k_usb_setup_pipe_resources`:
>>
>> for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
>>         endpoint = &iface_desc->endpoint[i].desc;
>>
>>         // get the address from endpoint descriptor
>>         pipe_num = ath10k_usb_get_logical_pipe_num(ar_usb,
>>                                                 endpoint->bEndpointAddress,
>>                                                 &urbcount);
>>         ......
>>         // select the pipe object
>>         pipe = &ar_usb->pipes[pipe_num];
>>
>>         // initialize the ar_usb field
>>         pipe->ar_usb = ar_usb;
>> }
>>
>> The driver assumes that the addresses reported in endpoint
>> descriptors from device side  to be complete. If a device is
>> malicious and does not report complete addresses, it may trigger
>> NULL-ptr-deref `ath10k_usb_alloc_urb_from_pipe` and
>> `ath10k_usb_free_urb_to_pipe`.
>>
>> This patch fixes the bug by preventing potential NULL-ptr-deref.
>>
>> Signed-off-by: Hui Peng <benquike@xxxxxxxxx>
>> Reported-by: Hui Peng <benquike@xxxxxxxxx>
>> Reported-by: Mathias Payer <mathias.payer@xxxxxxxxxxxxx>
> This patch fixes CVE-2019-15099, which has CVSS scores of 7.5 (CVSS 3.0)
> and 7.8 (CVSS 2.0). Yet, I don't find it in the upstream kernel or in Linux
> next.
>
> Is the patch going to be applied to the upstream kernel anytime soon ? If
> not, is there reason to believe that its severity may not be as high as the
> CVSS score indicates ?
The score was assigned by MITRE.
Same as previous ones, it is under review, once passed, it will be applied.
> Thanks,
> Guenter
>
>> ---
>>  drivers/net/wireless/ath/ath10k/usb.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/net/wireless/ath/ath10k/usb.c b/drivers/net/wireless/ath/ath10k/usb.c
>> index e1420f67f776..14d86627b47f 100644
>> --- a/drivers/net/wireless/ath/ath10k/usb.c
>> +++ b/drivers/net/wireless/ath/ath10k/usb.c
>> @@ -38,6 +38,10 @@ ath10k_usb_alloc_urb_from_pipe(struct ath10k_usb_pipe *pipe)
>>  	struct ath10k_urb_context *urb_context = NULL;
>>  	unsigned long flags;
>>  
>> +	/* bail if this pipe is not initialized */
>> +	if (!pipe->ar_usb)
>> +		return NULL;
>> +
>>  	spin_lock_irqsave(&pipe->ar_usb->cs_lock, flags);
>>  	if (!list_empty(&pipe->urb_list_head)) {
>>  		urb_context = list_first_entry(&pipe->urb_list_head,
>> @@ -55,6 +59,10 @@ static void ath10k_usb_free_urb_to_pipe(struct ath10k_usb_pipe *pipe,
>>  {
>>  	unsigned long flags;
>>  
>> +	/* bail if this pipe is not initialized */
>> +	if (!pipe->ar_usb)
>> +		return NULL;
>> +
>>  	spin_lock_irqsave(&pipe->ar_usb->cs_lock, flags);
>>  
>>  	pipe->urb_cnt++;
>> -- 
>> 2.22.0
>>