diff options
| author | Takashi Iwai <tiwai@suse.de> | 2018-04-26 09:17:45 +0200 |
|---|---|---|
| committer | Sasha Levin <alexander.levin@microsoft.com> | 2018-05-22 21:36:39 -0400 |
| commit | 105ab3b63f3525fd2d234c24d43c9226162b22ae (patch) | |
| tree | 18610c0f5bfe19085f512d57cf44e48a7cfa9f7e | |
| parent | 1d139fd4a10bc8d4352e9805fb4a5bbe4e1f1409 (diff) | |
ALSA: seq: Fix races at MIDI encoding in snd_virmidi_output_trigger()
[ Upstream commit 8f22e52528cc372b218b5f100457469615c733ce ]
The sequencer virmidi code has an open race at its output trigger
callback: namely, virmidi keeps only one event packet for processing
while it doesn't protect for concurrent output trigger calls.
snd_virmidi_output_trigger() tries to process the previously
unfinished event before starting encoding the given MIDI stream, but
this is done without any lock. Meanwhile, if another rawmidi stream
starts the output trigger, this proceeds further, and overwrites the
event package that is being processed in another thread. This
eventually corrupts and may lead to the invalid memory access if the
event type is like SYSEX.
The fix is just to move the spinlock to cover both the pending event
and the new stream.
The bug was spotted by a new fuzzer, RaceFuzzer.
BugLink: http://lkml.kernel.org/r/20180426045223.GA15307@dragonet.kaist.ac.kr
Reported-by: DaeRyong Jeong <threeearcat@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
| -rw-r--r-- | sound/core/seq/seq_virmidi.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c index 3b126af4a026..ef494ffc1369 100644 --- a/sound/core/seq/seq_virmidi.c +++ b/sound/core/seq/seq_virmidi.c @@ -174,12 +174,12 @@ static void snd_virmidi_output_trigger(struct snd_rawmidi_substream *substream, } return; } + spin_lock_irqsave(&substream->runtime->lock, flags); if (vmidi->event.type != SNDRV_SEQ_EVENT_NONE) { if (snd_seq_kernel_client_dispatch(vmidi->client, &vmidi->event, in_atomic(), 0) < 0) - return; + goto out; vmidi->event.type = SNDRV_SEQ_EVENT_NONE; } - spin_lock_irqsave(&substream->runtime->lock, flags); while (1) { count = __snd_rawmidi_transmit_peek(substream, buf, sizeof(buf)); if (count <= 0) |