This is a note to let you know that I've just added the patch titled
sound/oss: fix deadlock in sequencer_ioctl(SNDCTL_SEQ_OUTOFBAND)
to the 4.0-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:
sound-oss-fix-deadlock-in-sequencer_ioctl-sndctl_seq_outofband.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From bc26d4d06e337ade069f33d3f4377593b24e6e36 Mon Sep 17 00:00:00 2001
From: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
Date: Sat, 18 Apr 2015 02:53:25 +0300
Subject: sound/oss: fix deadlock in sequencer_ioctl(SNDCTL_SEQ_OUTOFBAND)
From: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
commit bc26d4d06e337ade069f33d3f4377593b24e6e36 upstream.
A deadlock can be initiated by userspace via ioctl(SNDCTL_SEQ_OUTOFBAND)
on /dev/sequencer with TMR_ECHO midi event.
In this case the control flow is:
sound_ioctl()
-> case SND_DEV_SEQ:
case SND_DEV_SEQ2:
sequencer_ioctl()
-> case SNDCTL_SEQ_OUTOFBAND:
spin_lock_irqsave(&lock,flags);
play_event();
-> case EV_TIMING:
seq_timing_event()
-> case TMR_ECHO:
seq_copy_to_input()
-> spin_lock_irqsave(&lock,flags);
It seems that spin_lock_irqsave() around play_event() is not necessary,
because the only other call location in seq_startplay() makes the call
without acquiring spinlock.
So, the patch just removes spinlocks around play_event().
By the way, it removes unreachable code in seq_timing_event(),
since (seq_mode == SEQ_2) case is handled in the beginning.
Compile tested only.
Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Cc: Willy Tarreau <w@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/oss/sequencer.c | 12 ++----------
1 file changed, 2 insertions(+), 10 deletions(-)
--- a/sound/oss/sequencer.c
+++ b/sound/oss/sequencer.c
@@ -681,13 +681,8 @@ static int seq_timing_event(unsigned cha
break;
case TMR_ECHO:
- if (seq_mode == SEQ_2)
- seq_copy_to_input(event_rec, 8);
- else
- {
- parm = (parm << 8 | SEQ_ECHO);
- seq_copy_to_input((unsigned char *) &parm, 4);
- }
+ parm = (parm << 8 | SEQ_ECHO);
+ seq_copy_to_input((unsigned char *) &parm, 4);
break;
default:;
@@ -1324,7 +1319,6 @@ int sequencer_ioctl(int dev, struct file
int mode = translate_mode(file);
struct synth_info inf;
struct seq_event_rec event_rec;
- unsigned long flags;
int __user *p = arg;
orig_dev = dev = dev >> 4;
@@ -1479,9 +1473,7 @@ int sequencer_ioctl(int dev, struct file
case SNDCTL_SEQ_OUTOFBAND:
if (copy_from_user(&event_rec, arg, sizeof(event_rec)))
return -EFAULT;
- spin_lock_irqsave(&lock,flags);
play_event(event_rec.arr);
- spin_unlock_irqrestore(&lock,flags);
return 0;
case SNDCTL_MIDI_INFO:
Patches currently in stable-queue which might be from khoroshilov@xxxxxxxxx are
queue-4.0/sound-oss-fix-deadlock-in-sequencer_ioctl-sndctl_seq_outofband.patch
--
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