[PATCH][next] ALSA: 6fire: Fix undefined behavior bug in struct midi_runtime

[PATCH][next] ALSA: 6fire: Fix undefined behavior bug in struct midi_runtime

[Gustavo A. R. Silva]

`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@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.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

Re: [PATCH][next] ALSA: 6fire: Fix undefined behavior bug in struct midi_runtime

[Kees Cook]

On Fri, Sep 29, 2023 at 06:06:32PM +0200, Gustavo A. R. Silva wrote:
> `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@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Another good find. :)

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH][next] ALSA: 6fire: Fix undefined behavior bug in struct midi_runtime

[Gustavo A. R. Silva]

On 9/29/23 19:27, Kees Cook wrote:
> On Fri, Sep 29, 2023 at 06:06:32PM +0200, Gustavo A. R. Silva wrote:
>> `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@vger.kernel.org
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> Another good find. :)

There are more coming. :)

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 

Thanks!
--
Gustavo

Re: [PATCH][next] ALSA: 6fire: Fix undefined behavior bug in struct midi_runtime

[Takashi Iwai]

On Fri, 29 Sep 2023 18:06:32 +0200,
Gustavo A. R. Silva wrote:
> 
> `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@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

The same question as your another 6fire patch is applied here: does it
"fix" anything real?


thanks,

Takashi

> ---
>  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
>