[PATCH 4.9 33/62] ath6kl: fix a NULL-ptr-deref bug in ath6kl_usb_alloc_urb_from_pipe()

Greg Kroah-Hartman
2019-11-04T22:27:10Z

From: Hui Peng <benquike@gmail.com>

[ Upstream commit 39d170b3cb62ba98567f5c4f40c27b5864b304e5 ]

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
(CVE-2019-15098).

Signed-off-by: Hui Peng <benquike@gmail.com>
Reported-by: Hui Peng <benquike@gmail.com>
Reported-by: Mathias Payer <mathias.payer@nebelwelt.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 9da3594fd010d..fc22c5f479276 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++;

--
2.20.1