linux-kernel - [PATCH][next] ALSA: 6fire: Fix undefined behavior bug in struct midi

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Message-ID: <ZRb2CKHuaCu0u38i@work>
Date:   Fri, 29 Sep 2023 18:06:32 +0200
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Torsten Schenk <torsten.schenk@...o.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] ALSA: 6fire: Fix undefined behavior bug in struct
 midi_runtime

`struct urb` is a flexible structure, which means that it contains a
flexible-array member at the bottom. This could potentially lead to an
overwrite of the objects following `out_urb` in `struct midi_runtime`,
among them a function pointer.

Fix this by placing the declaration of object `out_urb` at the end of
`struct midi_runtime`.

Fixes: c6d43ba816d1 ("ALSA: usb/6fire - Driver for TerraTec DMX 6Fire USB")
Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 sound/usb/6fire/midi.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/usb/6fire/midi.h b/sound/usb/6fire/midi.h
index 47640c845903..df3f41913274 100644
--- a/sound/usb/6fire/midi.h
+++ b/sound/usb/6fire/midi.h
@@ -22,12 +22,12 @@ struct midi_runtime {
 	spinlock_t in_lock;
 	spinlock_t out_lock;
 	struct snd_rawmidi_substream *out;
-	struct urb out_urb;
 	u8 out_serial; /* serial number of out packet */
 	u8 *out_buffer;
 	int buffer_offset;
 
 	void (*in_received)(struct midi_runtime *rt, u8 *data, int length);
+	struct urb out_urb;
 };
 
 int usb6fire_midi_init(struct sfire_chip *chip);
-- 
2.34.1