Patch "ALSA: seq: Fix OSS sysex delivery in OSS emulation" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ALSA: seq: Fix OSS sysex delivery in OSS emulation

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     alsa-seq-fix-oss-sysex-delivery-in-oss-emulation.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 132d358b183ac6ad8b3fea32ad5e0663456d18d1 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 7 Nov 2017 16:05:24 +0100
Subject: ALSA: seq: Fix OSS sysex delivery in OSS emulation

From: Takashi Iwai <tiwai@suse.de>

commit 132d358b183ac6ad8b3fea32ad5e0663456d18d1 upstream.

The SYSEX event delivery in OSS sequencer emulation assumed that the
event is encoded in the variable-length data with the straight
buffering.  This was the normal behavior in the past, but during the
development, the chained buffers were introduced for carrying more
data, while the OSS code was left intact.  As a result, when a SYSEX
event with the chained buffer data is passed to OSS sequencer port,
it may end up with the wrong memory access, as if it were having a too
large buffer.

This patch addresses the bug, by applying the buffer data expansion by
the generic snd_seq_dump_var_event() helper function.

Reported-by: syzbot <syzkaller@googlegroups.com>
Reported-by: Mark Salyzyn <salyzyn@android.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/core/seq/oss/seq_oss_midi.c  |    4 +---
 sound/core/seq/oss/seq_oss_readq.c |   29 +++++++++++++++++++++++++++++
 sound/core/seq/oss/seq_oss_readq.h |    2 ++
 3 files changed, 32 insertions(+), 3 deletions(-)

--- a/sound/core/seq/oss/seq_oss_midi.c
+++ b/sound/core/seq/oss/seq_oss_midi.c
@@ -612,9 +612,7 @@ send_midi_event(struct seq_oss_devinfo *
 	if (!dp->timer->running)
 		len = snd_seq_oss_timer_start(dp->timer);
 	if (ev->type == SNDRV_SEQ_EVENT_SYSEX) {
-		if ((ev->flags & SNDRV_SEQ_EVENT_LENGTH_MASK) == SNDRV_SEQ_EVENT_LENGTH_VARIABLE)
-			snd_seq_oss_readq_puts(dp->readq, mdev->seq_device,
-					       ev->data.ext.ptr, ev->data.ext.len);
+		snd_seq_oss_readq_sysex(dp->readq, mdev->seq_device, ev);
 	} else {
 		len = snd_midi_event_decode(mdev->coder, msg, sizeof(msg), ev);
 		if (len > 0)
--- a/sound/core/seq/oss/seq_oss_readq.c
+++ b/sound/core/seq/oss/seq_oss_readq.c
@@ -118,6 +118,35 @@ snd_seq_oss_readq_puts(struct seq_oss_re
 }
 
 /*
+ * put MIDI sysex bytes; the event buffer may be chained, thus it has
+ * to be expanded via snd_seq_dump_var_event().
+ */
+struct readq_sysex_ctx {
+	struct seq_oss_readq *readq;
+	int dev;
+};
+
+static int readq_dump_sysex(void *ptr, void *buf, int count)
+{
+	struct readq_sysex_ctx *ctx = ptr;
+
+	return snd_seq_oss_readq_puts(ctx->readq, ctx->dev, buf, count);
+}
+
+int snd_seq_oss_readq_sysex(struct seq_oss_readq *q, int dev,
+			    struct snd_seq_event *ev)
+{
+	struct readq_sysex_ctx ctx = {
+		.readq = q,
+		.dev = dev
+	};
+
+	if ((ev->flags & SNDRV_SEQ_EVENT_LENGTH_MASK) != SNDRV_SEQ_EVENT_LENGTH_VARIABLE)
+		return 0;
+	return snd_seq_dump_var_event(ev, readq_dump_sysex, &ctx);
+}
+
+/*
  * copy an event to input queue:
  * return zero if enqueued
  */
--- a/sound/core/seq/oss/seq_oss_readq.h
+++ b/sound/core/seq/oss/seq_oss_readq.h
@@ -44,6 +44,8 @@ void snd_seq_oss_readq_delete(struct seq
 void snd_seq_oss_readq_clear(struct seq_oss_readq *readq);
 unsigned int snd_seq_oss_readq_poll(struct seq_oss_readq *readq, struct file *file, poll_table *wait);
 int snd_seq_oss_readq_puts(struct seq_oss_readq *readq, int dev, unsigned char *data, int len);
+int snd_seq_oss_readq_sysex(struct seq_oss_readq *q, int dev,
+			    struct snd_seq_event *ev);
 int snd_seq_oss_readq_put_event(struct seq_oss_readq *readq, union evrec *ev);
 int snd_seq_oss_readq_put_timestamp(struct seq_oss_readq *readq, unsigned long curt, int seq_mode);
 int snd_seq_oss_readq_pick(struct seq_oss_readq *q, union evrec *rec);


Patches currently in stable-queue which might be from tiwai@suse.de are

queue-4.4/alsa-seq-avoid-invalid-lockdep-class-warning.patch
queue-4.4/alsa-seq-fix-oss-sysex-delivery-in-oss-emulation.patch