linux-kernel - [PATCH 3.16 212/366] ALSA: seq: oss: Fix unbalanced use lock for synth MIDI device

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <lsq.1539530741.268757558@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Takashi Iwai" <tiwai@...e.de>
Subject: [PATCH 3.16 212/366] ALSA: seq: oss: Fix unbalanced use lock for
 synth MIDI device

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

commit f5e94b4c6ebdabe0f602d796e0430180927521a0 upstream.

When get_synthdev() is called for a MIDI device, it returns the fixed
midi_synth_dev without the use refcounting.  OTOH, the caller is
supposed to unreference unconditionally after the usage, so this would
lead to unbalanced refcount.

This patch corrects the behavior and keep up the refcount balance also
for the MIDI synth device.

Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 sound/core/seq/oss/seq_oss_synth.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/sound/core/seq/oss/seq_oss_synth.c
+++ b/sound/core/seq/oss/seq_oss_synth.c
@@ -363,10 +363,14 @@ get_synthdev(struct seq_oss_devinfo *dp,
 		return NULL;
 	if (! dp->synths[dev].opened)
 		return NULL;
-	if (dp->synths[dev].is_midi)
-		return &midi_synth_dev;
-	if ((rec = get_sdev(dev)) == NULL)
-		return NULL;
+	if (dp->synths[dev].is_midi) {
+		rec = &midi_synth_dev;
+		snd_use_lock_use(&rec->use_lock);
+	} else {
+		rec = get_sdev(dev);
+		if (!rec)
+			return NULL;
+	}
 	if (! rec->opened) {
 		snd_use_lock_free(&rec->use_lock);
 		return NULL;