On Fri, 29 Sep 2023 17:59:22 +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 `receiver` in `struct comm_runtime`,
> among them some function pointers.
>
> Fix this by placing the declaration of object `receiver` at the end of
> `struct comm_runtime`.
>
> Fixes: ddb6b5a96437 ("ALSA: 6fire: fix DMA issues with URB transfer_buffer usage")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Sorry for the late reply, as I've been (still) off since the last
week.
Through a quick glance, I don't mind much to apply this, but I still
wonder how this "fixes" anything. Does it silence compiler warnings
or such?
Certainly struct urb *may* have flex array, but in this case, it's
clearly not used, so it's fixed-size. And, even if we shuffle the
member to put to the last, it doesn't fix anything automagically
alone. If a flex array were used, it still leads to memory corruption
unless we implement the allocation properly. So I find the patch
description is somehow misleading.
thanks,
Takashi
> ---
> sound/usb/6fire/comm.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/usb/6fire/comm.h b/sound/usb/6fire/comm.h
> index 2447d7ecf179..ee81572a4eec 100644
> --- a/sound/usb/6fire/comm.h
> +++ b/sound/usb/6fire/comm.h
> @@ -19,7 +19,6 @@ enum /* settings for comm */
> struct comm_runtime {
> struct sfire_chip *chip;
>
> - struct urb receiver;
> u8 *receiver_buffer;
>
> u8 serial; /* urb serial */
> @@ -30,6 +29,7 @@ struct comm_runtime {
> int (*write8)(struct comm_runtime *rt, u8 request, u8 reg, u8 value);
> int (*write16)(struct comm_runtime *rt, u8 request, u8 reg,
> u8 vh, u8 vl);
> + struct urb receiver;
> };
>
> int usb6fire_comm_init(struct sfire_chip *chip);
> --
> 2.34.1
>
