[PATCH 4.14 015/229] ALSA: bcd2000: Fix a UAF bug on the error path of probing

Greg Kroah-Hartman
2022-08-23T09:29:23Z

From: Zheyu Ma <zheyuma97@gmail.com>

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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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
@@ -357,7 +357,8 @@ 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);