kernel/linux.git/sound/core/seq/seq_virmidi.c, branch linux-5.3.y

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156

2019-05-30T18:26:35+00:00

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details you should have received a copy of the gnu general public license along with this program if not write to the free software foundation inc 59 temple place suite 330 boston ma 02111 1307 usa extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 1334 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Allison Randal Reviewed-by: Richard Fontana Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070033.113240726@linutronix.de Signed-off-by: Greg Kroah-Hartman

ALSA: rawmidi: A lightweight function to discard pending bytes

2018-10-04T18:13:17+00:00

For discarding the pending bytes on rawmidi, we process with a loop of snd_rawmidi_transmit() which is just a waste of CPU power. Implement a lightweight API function to discard the pending bytes and the proceed the ring buffer instantly, and use it instead of open codes. Signed-off-by: Takashi Iwai

ALSA: seq: virmidi: Fix discarding the unsubscribed output

2018-08-14T20:50:52+00:00

The recent change to move the virmidi output processing to a work slightly modified the code to discard the unsubscribed outputs so that it works without a temporary buffer. However, this is actually buggy, and may spew a kernel warning due to the unexpected call of snd_rawmidi_transmit_ack(), as triggered by syzbot. This patch takes back to the original code in that part, use a temporary buffer and simply repeat snd_rawmidi_transmit(), in order to address the regression. Fixes: f7debfe54090 ("ALSA: seq: virmidi: Offload the output event processing") Reported-by: syzbot+ec5f605c91812d200367@syzkaller.appspotmail.com Signed-off-by: Takashi Iwai

ALSA: seq: Remove dead codes

2018-08-01T20:54:35+00:00

There are a few functions that have been commented out for ages. And also there are functions that do nothing but placeholders. Let's kill them. Signed-off-by: Takashi Iwai

ALSA: seq: Minor cleanup of MIDI event parser helpers

2018-08-01T20:54:35+00:00

snd_midi_event_encode_byte() can never fail, and it can return rather true/false. Change the return type to bool, adjust the argument to receive a MIDI byte as unsigned char, and adjust the comment accordingly. This allows callers to drop error checks, which simplifies the code. Meanwhile, snd_midi_event_encode() helper is used only in seq_midi.c, and it can be better folded into it. This will reduce the total amount of lines in the end. Signed-off-by: Takashi Iwai

ALSA: seq: virmidi: Use READ_ONCE/WRITE_ONCE() macros

2018-07-30T12:52:30+00:00

The trigger flag in vmidi object can be referred in different contexts concurrently, hence it's better to be put with READ_ONCE() and WRITE_ONCE() macros to assure the accesses. Signed-off-by: Takashi Iwai

ALSA: seq: virmidi: Offload the output event processing

2018-07-30T12:51:51+00:00

The virmidi sequencer stuff tries to translate the rawmidi bytes to sequencer events and deliver the packets at trigger callback. The amount of the whole process of these translations and deliveries depends on the incoming rawmidi bytes, and we have no limit for that; this was the cause of a CPU soft lockup that had been reported and fixed recently. Although we've fixed the soft lockup by putting the temporary unlock and cond_resched(), it's rather a quick band aid. In this patch, meanwhile, the event parsing and delivery process is offloaded to a dedicated work, and the trigger callback just kicks it off. It has three merits, at least: - The processing is always done in a sleepable context, which can assure the event delivery with non-atomic flag without hackish is_atomic() usage. - Other relevant codes can be simplified, reducing the lines - It makes me happier Signed-off-by: Takashi Iwai

ALSA: virmidi: Fix too long output trigger loop

2018-07-27T06:59:25+00:00

The virmidi output trigger tries to parse the all available bytes and process sequencer events as much as possible. In a normal situation, this is supposed to be relatively short, but a program may give a huge buffer and it'll take a long time in a single spin lock, which may eventually lead to a soft lockup. This patch simply adds a workaround, a cond_resched() call in the loop if applicable. A better solution would be to move the event processor into a work, but let's put a duct-tape quickly at first. Reported-and-tested-by: Dae R. Jeong Reported-by: syzbot+619d9f40141d826b097e@syzkaller.appspotmail.com Cc: Signed-off-by: Takashi Iwai

ALSA: seq: Fix races at MIDI encoding in snd_virmidi_output_trigger()

2018-04-27T15:50:37+00:00

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 Cc: Signed-off-by: Takashi Iwai

ALSA: seq: Fix copy_from_user() call inside lock

2017-10-09T12:10:13+00:00

The event handler in the virmidi sequencer code takes a read-lock for the linked list traverse, while it's calling snd_seq_dump_var_event() in the loop. The latter function may expand the user-space data depending on the event type. It eventually invokes copy_from_user(), which might be a potential dead-lock. The sequencer core guarantees that the user-space data is passed only with atomic=0 argument, but snd_virmidi_dev_receive_event() ignores it and always takes read-lock(). For avoiding the problem above, this patch introduces rwsem for non-atomic case, while keeping rwlock for atomic case. Also while we're at it: the superfluous irq flags is dropped in snd_virmidi_input_open(). Reported-by: Jia-Ju Bai Cc: Signed-off-by: Takashi Iwai