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

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