[BUG] ALSA: seq: a possible sleep-in-atomic-context bug in snd_virmidi_dev_receive_event()

[Jia-Ju Bai]

The driver may sleep while holding a read lock.
The function call path (from bottom to top) in Linux 4.19 is:

sound/core/seq/seq_memory.c, 96:
ÂÂÂ copy_from_user in snd_seq_dump_var_event
sound/core/seq/seq_virmidi.c, 97:
ÂÂÂ snd_seq_dump_var_event in snd_virmidi_dev_receive_event
sound/core/seq/seq_virmidi.c, 88:
ÂÂÂ _raw_read_lock in snd_virmidi_dev_receive_event

copy_from_user() can sleep at runtime.

I am not sure how to properly fix this possible bug, so I only report it.

This bug is found by a static analysis tool STCheck written by myself.


Best wishes,
Jia-Ju Bai