This is a note to let you know that I've just added the patch titled
ALSA: seq: Avoid invalid lockdep class warning
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: alsa-seq-avoid-invalid-lockdep-class-warning.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 stable@vger.kernel.org know about it.
From 3510c7aa069aa83a2de6dab2b41401a198317bdc Mon Sep 17 00:00:00 2001
From: Takashi Iwai tiwai@suse.de Date: Mon, 6 Nov 2017 20:16:50 +0100 Subject: ALSA: seq: Avoid invalid lockdep class warning
From: Takashi Iwai tiwai@suse.de
commit 3510c7aa069aa83a2de6dab2b41401a198317bdc upstream.
The recent fix for adding rwsem nesting annotation was using the given "hop" argument as the lock subclass key. Although the idea itself works, it may trigger a kernel warning like: BUG: looking up invalid subclass: 8 .... since the lockdep has a smaller number of subclasses (8) than we currently allow for the hops there (10).
The current definition is merely a sanity check for avoiding the too deep delivery paths, and the 8 hops are already enough. So, as a quick fix, just follow the max hops as same as the max lockdep subclasses.
Fixes: 1f20f9ff57ca ("ALSA: seq: Fix nested rwsem annotation for lockdep splat") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/sound/seq_kernel.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/include/sound/seq_kernel.h +++ b/include/sound/seq_kernel.h @@ -49,7 +49,8 @@ typedef union snd_seq_timestamp snd_seq_ #define SNDRV_SEQ_DEFAULT_CLIENT_EVENTS 200
/* max delivery path length */ -#define SNDRV_SEQ_MAX_HOPS 10 +/* NOTE: this shouldn't be greater than MAX_LOCKDEP_SUBCLASSES */ +#define SNDRV_SEQ_MAX_HOPS 8
/* max size of event size */ #define SNDRV_SEQ_MAX_EVENT_LEN 0x3fffffff
Patches currently in stable-queue which might be from tiwai@suse.de are
queue-4.4/alsa-seq-avoid-invalid-lockdep-class-warning.patch queue-4.4/alsa-seq-fix-oss-sysex-delivery-in-oss-emulation.patch