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%3Ba=su...

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