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authorAlexey Khoroshilov <khoroshilov@ispras.ru>2015-04-18 02:53:25 +0300
committerTakashi Iwai <tiwai@suse.de>2015-04-18 09:05:55 +0200
commitbc26d4d06e337ade069f33d3f4377593b24e6e36 (patch)
treef575da72a0288b57034db2c091cc67bfed7c0982
parent43c499dc2778b96e21ed14e1a71e7b117a0b406f (diff)
sound/oss: fix deadlock in sequencer_ioctl(SNDCTL_SEQ_OUTOFBAND)
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@ispras.ru> Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/oss/sequencer.c12
1 files changed, 2 insertions, 10 deletions
diff --git a/sound/oss/sequencer.c b/sound/oss/sequencer.c
index c0eea1d..f19da4b 100644
--- a/sound/oss/sequencer.c
+++ b/sound/oss/sequencer.c
@@ -681,13 +681,8 @@ static int seq_timing_event(unsigned char *event_rec)
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 *file, unsigned int cmd, void __user *a
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 *file, unsigned int cmd, void __user *a
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: