ALSA: bcd2000: Fix a UAF bug on the error path of probing

When the driver fails in snd_card_register() at probe time, it will free
the 'bcd2k->midi_out_urb' before killing it, which may cause a UAF bug.

The following log can reveal it:

[   50.727020] BUG: KASAN: use-after-free in bcd2000_input_complete+0x1f1/0x2e0 [snd_bcd2000]
[   50.727623] Read of size 8 at addr ffff88810fab0e88 by task swapper/4/0
[   50.729530] Call Trace:
[   50.732899]  bcd2000_input_complete+0x1f1/0x2e0 [snd_bcd2000]

Fix this by adding usb_kill_urb() before usb_free_urb().

Fixes: 6f250d1daa14 ("ALSA: MIDI driver for Behringer BCD2000 USB device")
Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220715010515.2087925-1-zheyuma97@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/bcd2000/bcd2000.c b/sound/usb/bcd2000/bcd2000.c
index cd4a0bc6d278fd4d82d6895bc622fcfeff2ae12a..7aec0a95c609a951252105e60b5aa1622e1c39ac 100644 (file)
--- a/sound/usb/bcd2000/bcd2000.c
+++ b/sound/usb/bcd2000/bcd2000.c
@@ -348,7 +348,8 @@ static int bcd2000_init_midi(struct bcd2000 *bcd2k)
 static void bcd2000_free_usb_related_resources(struct bcd2000 *bcd2k,
                                                struct usb_interface *interface)
 {
-       /* usb_kill_urb not necessary, urb is aborted automatically */
+       usb_kill_urb(bcd2k->midi_out_urb);
+       usb_kill_urb(bcd2k->midi_in_urb);
 
        usb_free_urb(bcd2k->midi_out_urb);
        usb_free_urb(bcd2k->midi_in_urb);