[PATCH] usb: gadget: midi2: Fix the jack descriptor array sizes

[Takashi Iwai]

The jack in/out descriptor arrays in struct f_midi2_usb_config have
the size of MAX_CABLES, which look reasonable -- but it turned out to
be incorrect.  Namely, the entries for those arrays are added from
both inputs and outputs, hence for each loop cycle, it adds two, ended
up with as twice as the expected size.  This inconsistency may result
in potential OOB when a large number of jacks are set up via configfs,
although the max number of cables (the loop count) is limited to
MAX_CABLES.

For addressing it, correct the jack_ins & jack_outs array sizes to
twice, MAX_CABLES * 2.

Fixes: 856fa444b098 ("usb: gadget: midi2: Dynamically create MIDI 1.0 altset descriptors")
Reported-by: syzbot+c35f34092a4bc9855be6@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=c35f34092a4bc9855be6
Link: https://lore.kernel.org/20260826134606.127250-1-eadavis@xxxxxxxx
Cc: Edward Adam Davis <eadavis@xxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
 drivers/usb/gadget/function/f_midi2.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_midi2.c b/drivers/usb/gadget/function/f_midi2.c
index a4b72a6fad8a..091e9220fcbb 100644
--- a/drivers/usb/gadget/function/f_midi2.c
+++ b/drivers/usb/gadget/function/f_midi2.c
@@ -1634,8 +1634,8 @@ struct f_midi2_usb_config {
 
 	/* MIDI 1.0 jacks */
 	unsigned char jack_in, jack_out, jack_id;
-	struct usb_midi_in_jack_descriptor jack_ins[MAX_CABLES];
-	struct usb_midi_out_jack_descriptor_1 jack_outs[MAX_CABLES];
+	struct usb_midi_in_jack_descriptor jack_ins[MAX_CABLES * 2];
+	struct usb_midi_out_jack_descriptor_1 jack_outs[MAX_CABLES * 2];
 };
 
 static int append_config(struct f_midi2_usb_config *config, void *d)
-- 
2.55.0