[PATCH 4.9 027/101] ALSA: bcd2000: Fix a UAF bug on the error path of probing

[Greg Kroah-Hartman]

From: Zheyu Ma <zheyuma97@xxxxxxxxx>

commit ffb2759df7efbc00187bfd9d1072434a13a54139 upstream.

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: b47a22290d58 ("ALSA: MIDI driver for Behringer BCD2000 USB device")
Signed-off-by: Zheyu Ma <zheyuma97@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220715010515.2087925-1-zheyuma97@xxxxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 sound/usb/bcd2000/bcd2000.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/sound/usb/bcd2000/bcd2000.c
+++ b/sound/usb/bcd2000/bcd2000.c
@@ -350,7 +350,8 @@ static int bcd2000_init_midi(struct bcd2
 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);