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

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:     copy_from_user in snd_seq_dump_var_event sound/core/seq/seq_virmidi.c, 97:     snd_seq_dump_var_event in snd_virmidi_dev_receive_event sound/core/seq/seq_virmidi.c, 88:     _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