From: Takashi Iwai <tiwai@xxxxxxx> commit 05ca447630334c323c9e2b788b61133ab75d60d3 upstream. The initialization of MIDI devices that are found on some LINE6 drivers are currently done in a racy way; namely, the MIDI buffer instance is allocated and initialized in each private_init callback while the communication with the interface is already started via line6_init_cap_control() call before that point. This may lead to Oops in line6_data_received() when a spurious event is received, as reported by syzkaller. This patch moves the MIDI initialization to line6_init_cap_control() as well instead of the too-lately-called private_init for avoiding the race. Also this reduces slightly more lines, so it's a win-win change. Reported-by: syzbot+0d2b3feb0a2887862e06@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/000000000000a4be9405c28520de@xxxxxxxxxx Link: https://lore.kernel.org/r/20210517132725.GA50495@hyeyoo Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210518083939.1927-1-tiwai@xxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/usb/line6/driver.c | 4 ++++ sound/usb/line6/pod.c | 5 ----- sound/usb/line6/variax.c | 6 ------ 3 files changed, 4 insertions(+), 11 deletions(-) --- a/sound/usb/line6/driver.c +++ b/sound/usb/line6/driver.c @@ -699,6 +699,10 @@ static int line6_init_cap_control(struct line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL); if (!line6->buffer_message) return -ENOMEM; + + ret = line6_init_midi(line6); + if (ret < 0) + return ret; } else { ret = line6_hwdep_init(line6); if (ret < 0) --- a/sound/usb/line6/pod.c +++ b/sound/usb/line6/pod.c @@ -376,11 +376,6 @@ static int pod_init(struct usb_line6 *li if (err < 0) return err; - /* initialize MIDI subsystem: */ - err = line6_init_midi(line6); - if (err < 0) - return err; - /* initialize PCM subsystem: */ err = line6_init_pcm(line6, &pod_pcm_properties); if (err < 0) --- a/sound/usb/line6/variax.c +++ b/sound/usb/line6/variax.c @@ -159,7 +159,6 @@ static int variax_init(struct usb_line6 const struct usb_device_id *id) { struct usb_line6_variax *variax = line6_to_variax(line6); - int err; line6->process_message = line6_variax_process_message; line6->disconnect = line6_variax_disconnect; @@ -172,11 +171,6 @@ static int variax_init(struct usb_line6 if (variax->buffer_activate == NULL) return -ENOMEM; - /* initialize MIDI subsystem: */ - err = line6_init_midi(&variax->line6); - if (err < 0) - return err; - /* initiate startup procedure: */ schedule_delayed_work(&line6->startup_work, msecs_to_jiffies(VARIAX_STARTUP_DELAY1));
