Overview
In the Linux kernel, the following vulnerability has been resolved:
ALSA: us122l: Use snd_card_free_when_closed() at disconnection
The USB disconnect callback is supposed to be short and not too-long
waiting. OTOH, the current code uses snd_card_free() at
disconnection, but this waits for the close of all used fds, hence it
can take long. It eventually blocks the upper layer USB ioctls, which
may trigger a soft lockup.
An easy workaround is to replace snd_card_free() with
snd_card_free_when_closed(). This variant returns immediately while
the release of resources is done asynchronously by the card device
release at the last close.
The loop of us122l->mmap_count check is dropped as well. The check is
useless for the asynchronous operation with *_when_closed().