[PATCH] ALSA: rawmidi: Another workaround for false-positive mutex lockdep warning

[PATCH] ALSA: rawmidi: Another workaround for false-positive mutex lockdep warning

[Takashi Iwai]

While we attempted to work around the false-positive lockdep warning
due to the nested mutex lock in rawmidi at the open path for a UMP
legacy rawmidi, it didn't cover the similar locking at its close path,
and this still caused another false-positive reports by syzkaller.

Add a similar workaround to snd_rawmidi_kernel_release() as done in
the former commit 9c04742e73b3 ("ALSA: rawmidi: Work around
false-positive mutex lockdep warning") to cover completely.

Reported-by: syzbot+7d1edf0ff6a05961020c@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/6a8c7e4d.4d75e56a.c9a88.0052.GAE@google.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 include/sound/rawmidi.h | 8 +++++++-
 sound/core/rawmidi.c    | 9 ++++++---
 sound/core/ump.c        | 3 ++-
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/include/sound/rawmidi.h b/include/sound/rawmidi.h
index 88a6159364d0..4154035af414 100644
--- a/include/sound/rawmidi.h
+++ b/include/sound/rawmidi.h
@@ -179,7 +179,8 @@ int snd_rawmidi_info_select(struct snd_card *card, struct snd_rawmidi_info *info
 int snd_rawmidi_kernel_open_nested(struct snd_rawmidi *rmidi, int subdevice,
 				   int mode, struct snd_rawmidi_file *rfile,
 				   int depth);
-int snd_rawmidi_kernel_release(struct snd_rawmidi_file *rfile);
+int snd_rawmidi_kernel_release_nested(struct snd_rawmidi_file *rfile,
+				      int depth);
 int snd_rawmidi_output_params(struct snd_rawmidi_substream *substream,
 			      struct snd_rawmidi_params *params);
 int snd_rawmidi_input_params(struct snd_rawmidi_substream *substream,
@@ -201,6 +202,11 @@ static inline int snd_rawmidi_kernel_open(struct snd_rawmidi *rmidi,
 	return snd_rawmidi_kernel_open_nested(rmidi, subdevice, mode, rfile, 0);
 }
 
+static inline int snd_rawmidi_kernel_release(struct snd_rawmidi_file *rfile)
+{
+	return snd_rawmidi_kernel_release_nested(rfile, 0);
+}
+
 /* set up the tied devices */
 static inline void snd_rawmidi_tie_devices(struct snd_rawmidi *r1,
 					   struct snd_rawmidi *r2)
diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index bf504e27f73e..b688fd76f5d5 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -571,7 +571,6 @@ static void rawmidi_release_priv(struct snd_rawmidi_file *rfile)
 	struct snd_rawmidi *rmidi;
 
 	rmidi = rfile->rmidi;
-	guard(mutex)(&rmidi->open_mutex);
 	if (rfile->input) {
 		close_substream(rmidi, rfile->input, 1);
 		rfile->input = NULL;
@@ -585,7 +584,8 @@ static void rawmidi_release_priv(struct snd_rawmidi_file *rfile)
 }
 
 /* called from sound/core/seq/seq_midi.c */
-int snd_rawmidi_kernel_release(struct snd_rawmidi_file *rfile)
+int snd_rawmidi_kernel_release_nested(struct snd_rawmidi_file *rfile,
+				      int depth)
 {
 	struct snd_rawmidi *rmidi;
 
@@ -593,7 +593,9 @@ int snd_rawmidi_kernel_release(struct snd_rawmidi_file *rfile)
 		return -ENXIO;
 
 	rmidi = rfile->rmidi;
+	mutex_lock_nested(&rmidi->open_mutex, depth);
 	rawmidi_release_priv(rfile);
+	mutex_unlock(&rmidi->open_mutex);
 	module_put(rmidi->card->module);
 	return 0;
 }
@@ -607,7 +609,8 @@ static int snd_rawmidi_release(struct inode *inode, struct file *file)
 
 	rfile = file->private_data;
 	rmidi = rfile->rmidi;
-	rawmidi_release_priv(rfile);
+	scoped_guard(mutex, &rmidi->open_mutex)
+		rawmidi_release_priv(rfile);
 	kfree(rfile);
 	module = rmidi->card->module;
 	snd_card_file_remove(rmidi->card, file);
diff --git a/sound/core/ump.c b/sound/core/ump.c
index 82ad155c56e6..d183c8a000bd 100644
--- a/sound/core/ump.c
+++ b/sound/core/ump.c
@@ -1184,7 +1184,8 @@ static int snd_ump_legacy_close(struct snd_rawmidi_substream *substream)
 		ump->legacy_substreams[dir][group] = NULL;
 	if (dir == SNDRV_RAWMIDI_STREAM_OUTPUT) {
 		if (!--ump->legacy_out_opens)
-			snd_rawmidi_kernel_release(&ump->legacy_out_rfile);
+			snd_rawmidi_kernel_release_nested(&ump->legacy_out_rfile,
+							  SINGLE_DEPTH_NESTING);
 	}
 	return 0;
 }
-- 
2.55.0