linux-kernel - Re: [PATCH 4.19 06/48] 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: <20200810163717.GA24408@amd>
Date:   Mon, 10 Aug 2020 18:37:17 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.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: Re: [PATCH 4.19 06/48] ALSA: seq: oss: Serialize ioctls

Hi!

> 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.

That really is a "big hammer". And I believe it is too big.

In particular, do we need to drop the lock while sleeping in
SNDCTL_SEQ_SYNC: => snd_seq_oss_writeq_sync ?

Best regards,
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

Download attachment "signature.asc" of type "application/pgp-signature" (182 bytes)