usb: gadget: f_midi: fix MIDI Streaming descriptor lengths

commit da1668997052ed1cb00322e1f3b63702615c9429 upstream.

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 fddf539008a99a8f5c26a6f1ee237d5b46ace32b..1d8521103b6618a08c488b2094876826b32fcb70 100644 (file)
--- a/drivers/usb/gadget/function/f_midi.c
+++ b/drivers/usb/gadget/function/f_midi.c
@@ -999,11 +999,11 @@ 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;