usb: gadget: f_midi: fix MIDI Streaming descriptor lengths

While the MIDI jacks are configured correctly, and the MIDIStreaming
endpoint descriptors are filled with the correct information,
bNumEmbMIDIJack and bLength are set incorrectly in these descriptors.

This does not matter when the numbers of in and out ports are equal, but
when they differ the host will receive broken descriptors with
uninitialized stack memory leaking into the descriptor for whichever
value is smaller.

The precise meaning of "in" and "out" in the port counts is not clearly
defined and can be confusing.  But elsewhere the driver consistently
uses this to match the USB meaning of IN and OUT viewed from the host,
so that "in" ports send data to the host and "out" ports receive data
from it.

Cc: stable <stable@kernel.org>
Fixes: c8933c3f79568 ("USB: gadget: f_midi: allow a dynamic number of input and output ports")
Signed-off-by: John Keeping <jkeeping@inmusicbrands.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20250130195035.3883857-1-jkeeping@inmusicbrands.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
index 9b991cf5b0f8b61061e8846557679beaf894dbc5..47260d65066a89384ec0b9c353def8a094195bf9 100644 (file)
--- a/drivers/usb/gadget/function/f_midi.c
+++ b/drivers/usb/gadget/function/f_midi.c
@@ -1009,11 +1009,11 @@ static int f_midi_bind(struct usb_configuration *c, struct usb_function *f)
        }
 
        /* configure the endpoint descriptors ... */
-       ms_out_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->in_ports);
-       ms_out_desc.bNumEmbMIDIJack = midi->in_ports;
+       ms_out_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->out_ports);
+       ms_out_desc.bNumEmbMIDIJack = midi->out_ports;
 
-       ms_in_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->out_ports);
-       ms_in_desc.bNumEmbMIDIJack = midi->out_ports;
+       ms_in_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->in_ports);
+       ms_in_desc.bNumEmbMIDIJack = midi->in_ports;
 
        /* ... and add them to the list */
        endpoint_descriptor_index = i;