ALSA: rawmidi: Work around false-positive mutex lockdep warning

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When opening a legacy rawmidi device for a UMP, it may re-open an
existing rawmidi device for appending to a substream, leading to a
lockdep warning due to rmidi->open_mutex taken twice -- but the
rawmidi devices are completely individual, hence it's a
false-positive.

For avoiding the warning, modify the helper to open a rawmidi instance
with a proper locking subclass from the UMP legacy open.

Unfortunately, there is no good way to achieve it with guard(), so
reverted to the manual mutex calls again.

Reported-by: syzbot+d10d58fc99caa0489796@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/6a6a9634.57649fcc.360844.000b.GAE@google.com
Link: https://patch.msgid.link/20260806101352.1291581-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

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This commit is contained in:

Takashi Iwai 2026-08-06 12:13:51 +02:00

parent 02442d5fe8

commit 9c04742e73

3 changed files with 24 additions and 11 deletions

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14

include/sound/rawmidi.h

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12

sound/core/rawmidi.c

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9

sound/core/ump.c

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