linux-kernel - [PATCH AUTOSEL 4.9 04/17] Revert "ALSA: seq: Protect in-kernel ioctl calls with mutex"

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Message-Id: <20190604232459.7745-4-sashal@kernel.org>
Date:   Tue,  4 Jun 2019 19:24:45 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Takashi Iwai <tiwai@...e.de>,
        syzbot+47ded6c0f23016cde310@...kaller.appspotmail.com,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.9 04/17] Revert "ALSA: seq: Protect in-kernel ioctl calls with mutex"

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

[ Upstream commit f0654ba94e33699b295ce4f3dc73094db6209035 ]

This reverts commit feb689025fbb6f0aa6297d3ddf97de945ea4ad32.

The fix attempt was incorrect, leading to the mutex deadlock through
the close of OSS sequencer client.  The proper fix needs more
consideration, so let's revert it now.

Fixes: feb689025fbb ("ALSA: seq: Protect in-kernel ioctl calls with mutex")
Reported-by: syzbot+47ded6c0f23016cde310@...kaller.appspotmail.com
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/core/seq/seq_clientmgr.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 881c965555c5..bc6d371031fc 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -2348,19 +2348,14 @@ int snd_seq_kernel_client_ctl(int clientid, unsigned int cmd, void *arg)
 {
 	const struct ioctl_handler *handler;
 	struct snd_seq_client *client;
-	int err;
 
 	client = clientptr(clientid);
 	if (client == NULL)
 		return -ENXIO;
 
 	for (handler = ioctl_handlers; handler->cmd > 0; ++handler) {
-		if (handler->cmd == cmd) {
-			mutex_lock(&client->ioctl_mutex);
-			err = handler->func(client, arg);
-			mutex_unlock(&client->ioctl_mutex);
-			return err;
-		}
+		if (handler->cmd == cmd)
+			return handler->func(client, arg);
 	}
 
 	pr_debug("ALSA: seq unknown ioctl() 0x%x (type='%c', number=0x%02x)\n",
-- 
2.20.1