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ALSA: seq: Avoid invalid lockdep class warning

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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: 1f20f9ff57 ("ALSA: seq: Fix nested rwsem annotation for lockdep splat")
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2017-11-06 20:16:50 +01:00
parent 9b7d869ee5
commit 3510c7aa06
1 changed files with 2 additions and 1 deletions
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3
include/sound/seq_kernel.h
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@ -49,7 +49,8 @@ typedef union snd_seq_timestamp snd_seq_timestamp_t;
#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