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List:       linux-kernel
Subject:    Re: [PATCH 1/2] Fix a NULL-ptr-deref bug in ath6kl_usb_alloc_urb_from_pipe
From:       Guenter Roeck <linux () roeck-us ! net>
Date:       2019-08-31 18:02:19
Message-ID: 20190831180219.GA20860 () roeck-us ! net
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On Sat, Aug 03, 2019 at 08:29:04PM -0400, Hui Peng wrote:
> The `ar_usb` field of `ath6kl_usb_pipe_usb_pipe` objects
> are initialized to point to the containing `ath6kl_usb` object
> according to endpoint descriptors read from the device side, as shown
> below in `ath6kl_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 = ath6kl_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 `ath6kl_usb_alloc_urb_from_pipe` and
> `ath6kl_usb_free_urb_to_pipe`.
> 
> This patch fixes the bug by preventing potential NULL-ptr-deref.
> 
> Signed-off-by: Hui Peng <benquike@gmail.com>
> Reported-by: Hui Peng <benquike@gmail.com>
> Reported-by: Mathias Payer <mathias.payer@nebelwelt.net>

I don't see this patch in the upstream kernel or in -next.

At the same time, it is supposed to fix CVE-2019-15098, which has
a CVSS v2.0 score of 7.8 (high).

Is this patch going to be applied to the upstream kernel ?  If not,
are there reasons to believe that the vulnerability is not as severe
as its CVSS score indicates ?

Thanks,
Guenter

> ---
>  drivers/net/wireless/ath/ath6kl/usb.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/net/wireless/ath/ath6kl/usb.c b/drivers/net/wireless/ath/ath6kl/usb.c
> index 4defb7a0330f..53b66e9434c9 100644
> --- a/drivers/net/wireless/ath/ath6kl/usb.c
> +++ b/drivers/net/wireless/ath/ath6kl/usb.c
> @@ -132,6 +132,10 @@ ath6kl_usb_alloc_urb_from_pipe(struct ath6kl_usb_pipe *pipe)
>  	struct ath6kl_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 =
> @@ -150,6 +154,10 @@ static void ath6kl_usb_free_urb_to_pipe(struct ath6kl_usb_pipe *pipe,
>  {
>  	unsigned long flags;
>  
> +	/* bail if this pipe is not initialized */
> +	if (!pipe->ar_usb)
> +		return;
> +
>  	spin_lock_irqsave(&pipe->ar_usb->cs_lock, flags);
>  	pipe->urb_cnt++;
>  
> -- 
> 2.22.0
> 
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