This is a note to let you know that I've just added the patch titled
ALSA: line6: Fix racy initialization of LINE6 MIDI
to the 5.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-line6-fix-racy-initialization-of-line6-midi.patch
and it can be found in the queue-5.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 05ca447630334c323c9e2b788b61133ab75d60d3 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Tue, 18 May 2021 10:39:39 +0200
Subject: ALSA: line6: Fix racy initialization of LINE6 MIDI
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));
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-5.12/alsa-intel8x0-don-t-update-period-unless-prepared.patch
queue-5.12/alsa-firewire-lib-fix-amdtp_packet-tracepoints-event-for-packet_index-field.patch
queue-5.12/alsa-line6-fix-racy-initialization-of-line6-midi.patch
queue-5.12/alsa-dice-fix-stream-format-for-tc-electronic-konnekt-live-at-high-sampling-transfer-frequency.patch
