From 58c1c30074a8d1179e17a0188cd695b2f416bf75 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 25 Aug 2026 15:49:31 +0200 Subject: [PATCH] ALSA: rawmidi: Another workaround for false-positive mutex lockdep warning 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 Link: https://patch.msgid.link/20260825134942.1289272-1-tiwai@suse.de Signed-off-by: Takashi Iwai --- include/sound/rawmidi.h | 8 +++++++- sound/core/rawmidi.c | 11 +++++++---- sound/core/ump.c | 3 ++- 3 files changed, 16 insertions(+), 6 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..34b4c7d6dbe6 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; @@ -593,11 +593,13 @@ 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; } -EXPORT_SYMBOL(snd_rawmidi_kernel_release); +EXPORT_SYMBOL(snd_rawmidi_kernel_release_nested); static int snd_rawmidi_release(struct inode *inode, struct file *file) { @@ -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; }