[ALSA] Fix potential NULL pointer dereference in echoaudio midi

Fix races between the timer handler and the close function.

Signed-off-by: Giuliano Pochini <pochini@shiny.it>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

1 files changed, 4 insertions, 2 deletions

diff --git a/sound/pci/echoaudio/midi.c b/sound/pci/echoaudio/midi.c
index e31f0f11e3a8..91f5bff66d3f 100644
--- a/sound/pci/echoaudio/midi.c
+++ b/sound/pci/echoaudio/midi.c
@@ -213,7 +213,7 @@ static void snd_echo_midi_output_write(unsigned long data)
         sent = bytes = 0;
         spin_lock_irqsave(&chip->lock, flags);
         chip->midi_full = 0;
-        if (chip->midi_out && !snd_rawmidi_transmit_empty(chip->midi_out)) {
+        if (!snd_rawmidi_transmit_empty(chip->midi_out)) {
                 bytes = snd_rawmidi_transmit_peek(chip->midi_out, buf,
                                                   MIDI_OUT_BUFFER_SIZE - 1);
                 DE_MID(("Try to send %d bytes...\n", bytes));
@@ -264,9 +264,11 @@ static void snd_echo_midi_output_trigger(struct snd_rawmidi_substream *substream
                 }
         } else {
                 if (chip->tinuse) {
-                        del_timer(&chip->timer);
                         chip->tinuse = 0;
+                        spin_unlock_irq(&chip->lock);
+                        del_timer_sync(&chip->timer);
                         DE_MID(("Timer removed\n"));
+                        return;
                 }
         }
         spin_unlock_irq(&chip->lock);