diff options
| author | Alexey Khoroshilov <khoroshilov@ispras.ru> | 2015-04-18 02:53:25 +0300 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-05-20 11:15:44 +0200 |
| commit | fae12cf4a9a5ba5dd95f3bc9dc39c75287d51414 (patch) | |
| tree | 41dbca5dbefede4b8ef0164b7e119f92c0919beb /sound | |
| parent | b1c8515067ef5a55542ae0fc114feb087fb0dd09 (diff) | |
| download | lwn-fae12cf4a9a5ba5dd95f3bc9dc39c75287d51414.tar.gz lwn-fae12cf4a9a5ba5dd95f3bc9dc39c75287d51414.zip | |
sound/oss: fix deadlock in sequencer_ioctl(SNDCTL_SEQ_OUTOFBAND)
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@ispras.ru>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'sound')
| -rw-r--r-- | sound/oss/sequencer.c | 12 |
1 files changed, 2 insertions, 10 deletions
diff --git a/sound/oss/sequencer.c b/sound/oss/sequencer.c index 4ff60a6427d9..2e67dd590be5 100644 --- a/sound/oss/sequencer.c +++ b/sound/oss/sequencer.c @@ -683,13 +683,8 @@ 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:; @@ -1332,7 +1327,6 @@ 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; @@ -1487,9 +1481,7 @@ 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: |