[PATCH v2] ath10k: Fix a NULL-ptr-deref bug in ath10k_usb_alloc_urb_from_pipe

[Guenter Roeck]

From: Hui Peng <benquike@xxxxxxxxx>

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>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[groeck: Add driver tag to subject, fix build warning]
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
v2: Fix build warning, add "ath10k:" to subject

 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..9ebe74ee4aef 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;
+
 	spin_lock_irqsave(&pipe->ar_usb->cs_lock, flags);
 
 	pipe->urb_cnt++;
-- 
2.17.1