[PATCH v2] wifi: zd1211rw: reject secondary interfaces to prevent conflicts

The zd1211rw driver is designed for single-function Wi-Fi dongles and
hardcodes its USB endpoints. When a malformed USB device exposes multiple
interfaces that match the driver's device ID, the driver blindly binds to
all of them.

During probe(), the driver calls usb_reset_device(), which iterates over
all interfaces and invokes the pre_reset() callback for each bound
interface. Since multiple interfaces are bound to zd1211rw, pre_reset() is
called sequentially for each instance, acquiring their respective
&mac->chip.mutex. Because all instances initialize their mutexes with the
same lock class, lockdep detects a task acquiring a lock of the same class
it already holds and flags it as a possible recursive deadlock:

WARNING: possible recursive locking detected
kworker/0:1/11 is trying to acquire lock:
ffff88810371dde0 (&chip->mutex){+.+.}-{4:4}, at:
zd_chip_disable_rxtx+0x20/0x50
drivers/net/wireless/zydas/zd1211rw/zd_chip.c:1465

but task is already holding lock:
ffff8881138ddde0 (&chip->mutex){+.+.}-{4:4}, at: pre_reset+0x28c/0x380
drivers/net/wireless/zydas/zd1211rw/zd_usb.c:1505

Fix this by explicitly rejecting secondary interfaces (bInterfaceNumber !=
0) during probe(). This ensures that only a single instance of the driver
binds to the device, eliminating the recursive locking scenario.

Fixes: e85d0918b54f ("[PATCH] ZyDAS ZD1211 USB-WLAN driver")
Assisted-by: Gemini:gemini-3.5-flash Gemini:gemini-3.1-pro-preview syzbot
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=0ec3d1a6cf1fbe79c153
Link: https://syzkaller.appspot.com/ai_job?id=00724ef7-fd77-4cde-9779-895b8f63c2f6
Signed-off-by: Slawomir Stepien <[email protected]>
---
v2:
* Fix the style of the block comment

v1:
* https://lore.kernel.org/all/[email protected]/T/
---
 drivers/net/wireless/zydas/zd1211rw/zd_usb.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/wireless/zydas/zd1211rw/zd_usb.c b/drivers/net/wireless/zydas/zd1211rw/zd_usb.c
index 966d8ccb0dbc..98102c663434 100644
--- a/drivers/net/wireless/zydas/zd1211rw/zd_usb.c
+++ b/drivers/net/wireless/zydas/zd1211rw/zd_usb.c
@@ -1353,6 +1353,14 @@ static int probe(struct usb_interface *intf, const struct usb_device_id *id)
 	struct zd_usb *usb;
 	struct ieee80211_hw *hw = NULL;
 
+	/*
+	 * ZD1211 devices are single-function. Reject secondary interfaces
+	 * to prevent multiple instances from conflicting on hardcoded endpoints
+	 * and triggering recursive locking warnings.
+	 */
+	if (intf->cur_altsetting->desc.bInterfaceNumber != 0)
+		return -ENODEV;
+
 	print_id(udev);
 
 	if (id->driver_info & DEVICE_INSTALLER)
-- 
2.55.0