[PATCH] usb: gadget: f_midi: initialize work in f_midi_alloc()

[Jeffin Philip]

f_midi_alloc initializes free_ref to 1 and it can only be incremented
when a sound card is registered via f_midi_register_card().
f_midi_register_card() is only called in f_midi_bind() which actually
performs INIT_WORK. If f_midi_bind() is never run, work is not
initialized and the if condition in f_midi_free becomes true,
this results in a warning later in __flush_work as work->func = 0.
Fix this by moving INIT_WORK from f_midi_bind() to f_midi_alloc().

Reported-by: syzbot+d5fa3d224505c8610702@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=d5fa3d224505c8610702
Fixes: 8653d71ce376 ("usb/gadget: f_midi: Replace tasklet with work")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jeffin Philip <jeffinphilip14@xxxxxxxxx>
---
 drivers/usb/gadget/function/f_midi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
index fba8cf787d6c..63fb6ee70a3d 100644
--- a/drivers/usb/gadget/function/f_midi.c
+++ b/drivers/usb/gadget/function/f_midi.c
@@ -879,7 +879,6 @@ static int f_midi_bind(struct usb_configuration *c, struct usb_function *f)
 	int status, n, jack = 1, i = 0, endpoint_descriptor_index = 0;
 
 	midi->gadget = cdev->gadget;
-	INIT_WORK(&midi->work, f_midi_in_work);
 	status = f_midi_register_card(midi);
 	if (status < 0)
 		goto fail_register;
@@ -1377,6 +1376,7 @@ static struct usb_function *f_midi_alloc(struct usb_function_instance *fi)
 		status = -ENOMEM;
 		goto midi_free;
 	}
+	INIT_WORK(&midi->work, f_midi_in_work);
 	midi->out_ports = opts->out_ports;
 	midi->index = opts->index;
 	midi->buflen = opts->buflen;
-- 
2.55.0