Bluetooth: btusb: mediatek: Avoid btusb_mtk_claim_iso_intf() NULL deref

commit c884a0b27b4586e607431d86a1aa0bb4fb39169c upstream.

In btusb_mtk_setup(), we set `btmtk_data->isopkt_intf` to:
  usb_ifnum_to_if(data->udev, MTK_ISO_IFNUM)

That function can return NULL in some cases. Even when it returns
NULL, though, we still go on to call btusb_mtk_claim_iso_intf().

As of commit e9087e828827 ("Bluetooth: btusb: mediatek: Add locks for
usb_driver_claim_interface()"), calling btusb_mtk_claim_iso_intf()
when `btmtk_data->isopkt_intf` is NULL will cause a crash because
we'll end up passing a bad pointer to device_lock(). Prior to that
commit we'd pass the NULL pointer directly to
usb_driver_claim_interface() which would detect it and return an
error, which was handled.

Resolve the crash in btusb_mtk_claim_iso_intf() by adding a NULL check
at the start of the function. This makes the code handle a NULL
`btmtk_data->isopkt_intf` the same way it did before the problematic
commit (just with a slight change to the error message printed).

Reported-by: IncogCyberpunk <incogcyberpunk@proton.me>
Closes: http://lore.kernel.org/r/a380d061-479e-4713-bddd-1d6571ca7e86@leemhuis.info
Fixes: e9087e828827 ("Bluetooth: btusb: mediatek: Add locks for usb_driver_claim_interface()")
Cc: stable@vger.kernel.org
Tested-by: IncogCyberpunk <incogcyberpunk@proton.me>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index b6c37e87c6a08fe30a046533edee514ba76fd317..dc0c45756c4487cca3373c447f28f2c99857baaa 100644 (file)
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -2714,6 +2714,11 @@ static void btusb_mtk_claim_iso_intf(struct btusb_data *data)
        if (!btmtk_data)
                return;
 
+       if (!btmtk_data->isopkt_intf) {
+               bt_dev_err(data->hdev, "Can't claim NULL iso interface");
+               return;
+       }
+
        /*
         * The function usb_driver_claim_interface() is documented to need
         * locks held if it's not called from a probe routine. The code here