sound: rawmidi: fix checking of O_APPEND when opening MIDI device

Commit 9a1b64caac82aa02cb74587ffc798e6f42c6170a in 2.6.30 dropped the
check that a substream must already have been opened with O_APPEND to be
able to open it a second time.

This would make it possible for a substream to be switched to append
mode, which would mean that non-atomic writes would fail unexpectedly.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index 3071e6f5801e..091405385e15 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -248,7 +248,8 @@ static int assign_substream(struct snd_rawmidi *rmidi, int subdevice,
         list_for_each_entry(substream, &s->substreams, list) {
                 if (substream->opened) {
                         if (stream == SNDRV_RAWMIDI_STREAM_INPUT ||
-                            !(mode & SNDRV_RAWMIDI_LFLG_APPEND))
+                            !(mode & SNDRV_RAWMIDI_LFLG_APPEND) ||
+                            !substream->append)
                                 continue;
                 }
                 if (subdevice < 0 || subdevice == substream->number) {