From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:52732 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751694AbdKEOpJ (ORCPT ); Sun, 5 Nov 2017 09:45:09 -0500 Subject: Patch "ALSA: seq: Fix nested rwsem annotation for lockdep splat" has been added to the 4.4-stable tree To: tiwai@suse.de, bot+7feb8de6b4d6bf810cf098bef942cc387e79d0ad@syzkaller.appspotmail.com, dvyukov@google.com, gregkh@linuxfoundation.org Cc: , From: Date: Sun, 05 Nov 2017 15:44:56 +0100 Message-ID: <150989309641134@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled ALSA: seq: Fix nested rwsem annotation for lockdep splat to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: alsa-seq-fix-nested-rwsem-annotation-for-lockdep-splat.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 1f20f9ff57ca23b9f5502fca85ce3977e8496cb1 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Sun, 29 Oct 2017 11:10:43 +0100 Subject: ALSA: seq: Fix nested rwsem annotation for lockdep splat From: Takashi Iwai commit 1f20f9ff57ca23b9f5502fca85ce3977e8496cb1 upstream. syzkaller reported the lockdep splat due to the possible deadlock of grp->list_mutex of each sequencer client object. Actually this is rather a false-positive report due to the missing nested lock annotations. The sequencer client may deliver the event directly to another client which takes another own lock. For addressing this issue, this patch replaces the simple down_read() with down_read_nested(). As a lock subclass, the already existing "hop" can be re-used, which indicates the depth of the call. Reference: http://lkml.kernel.org/r/089e082686ac9b482e055c832617@google.com Reported-by: syzbot Reported-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/seq/seq_clientmgr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -676,7 +676,7 @@ static int deliver_to_subscribers(struct if (atomic) read_lock(&grp->list_lock); else - down_read(&grp->list_mutex); + down_read_nested(&grp->list_mutex, hop); list_for_each_entry(subs, &grp->list_head, src_list) { /* both ports ready? */ if (atomic_read(&subs->ref_count) != 2) Patches currently in stable-queue which might be from tiwai@suse.de are queue-4.4/alsa-seq-fix-nested-rwsem-annotation-for-lockdep-splat.patch queue-4.4/alsa-timer-add-missing-mutex-lock-for-compat-ioctls.patch