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authorTakashi Iwai <tiwai@suse.de>2017-10-29 11:10:43 +0100
committerTakashi Iwai <tiwai@suse.de>2017-10-31 09:09:10 +0100
commit1f20f9ff57ca23b9f5502fca85ce3977e8496cb1 (patch)
tree51212012496d31592812a4bfafb4f782d3840e7e
parent79fb0518fec8c8b4ea7f1729f54f293724b3dbb0 (diff)
ALSA: seq: Fix nested rwsem annotation for lockdep splat
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 <bot+7feb8de6b4d6bf810cf098bef942cc387e79d0ad@syzkaller.appspotmail.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/core/seq/seq_clientmgr.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 6c9cba2166d9..d10c780dfd54 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -663,7 +663,7 @@ static int deliver_to_subscribers(struct snd_seq_client *client,
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)