linux-kernel - [PATCH 4.4 034/149] ALSA: seq: oss: Serialize ioctls

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: <20200820092127.381677453@linuxfoundation.org>
Date:   Thu, 20 Aug 2020 11:21:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+1a54a94bd32716796edd@...kaller.appspotmail.com,
        syzbot+9d2abfef257f3e2d4713@...kaller.appspotmail.com,
        Hillf Danton <hdanton@...a.com>, Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.4 034/149] ALSA: seq: oss: Serialize ioctls

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

commit 80982c7e834e5d4e325b6ce33757012ecafdf0bb upstream.

Some ioctls via OSS sequencer API may race and lead to UAF when the
port create and delete are performed concurrently, as spotted by a
couple of syzkaller cases.  This patch is an attempt to address it by
serializing the ioctls with the existing register_mutex.

Basically OSS sequencer API is an obsoleted interface and was designed
without much consideration of the concurrency.  There are very few
applications with it, and the concurrent performance isn't asked,
hence this "big hammer" approach should be good enough.

Reported-by: syzbot+1a54a94bd32716796edd@...kaller.appspotmail.com
Reported-by: syzbot+9d2abfef257f3e2d4713@...kaller.appspotmail.com
Suggested-by: Hillf Danton <hdanton@...a.com>
Cc: <stable@...r.kernel.org>
Link: https://lore.kernel.org/r/20200804185815.2453-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/core/seq/oss/seq_oss.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/sound/core/seq/oss/seq_oss.c
+++ b/sound/core/seq/oss/seq_oss.c
@@ -180,10 +180,16 @@ static long
 odev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct seq_oss_devinfo *dp;
+	long rc;
+
 	dp = file->private_data;
 	if (snd_BUG_ON(!dp))
 		return -ENXIO;
-	return snd_seq_oss_ioctl(dp, cmd, arg);
+
+	mutex_lock(&register_mutex);
+	rc = snd_seq_oss_ioctl(dp, cmd, arg);
+	mutex_unlock(&register_mutex);
+	return rc;
 }
 
 #ifdef CONFIG_COMPAT