Re: [PATCH] accel/ivpu: Fix signed integer truncation in IPC receive

[David Laight <david.laight.linux@gmail.com>]

On Fri, 29 May 2026 13:50:05 +0200
Andrzej Kacprowski <andrzej.kacprowski@linux.intel.com> wrote:

> Fix potential buffer overflow where firmware-supplied data_size is cast
> to signed int before being used in min_t(). Large unsigned values
> (>= 0x80000000) become negative, causing unsigned wraparound and  
> oversized memcpy operations that can overflow the stack buffer.
> 
> Change min_t(int, ...) to min_t(u32, ...) to ensure large values are
> properly clamped instead of becoming negative.

Just use min(), no need for the casts that min_t() adds.

This is another (slightly unusual) example of why min_t() is broken.
Even with min() doing strict type checks the correct fix would have been to
use (u32)sizeof(*jsm_msg) - and completely ignore what checkpatch says.

-- David

> 
> Fixes: 3b434a3445ff ("accel/ivpu: Use threaded IRQ to handle JOB done messages")
> Cc: <stable@vger.kernel.org> # v6.18+
> Signed-off-by: Andrzej Kacprowski <andrzej.kacprowski@linux.intel.com>
> ---
>  drivers/accel/ivpu/ivpu_ipc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/accel/ivpu/ivpu_ipc.c b/drivers/accel/ivpu/ivpu_ipc.c
> index f47df092bb0d..9980a7898bed 100644
> --- a/drivers/accel/ivpu/ivpu_ipc.c
> +++ b/drivers/accel/ivpu/ivpu_ipc.c
> @@ -276,7 +276,7 @@ int ivpu_ipc_receive(struct ivpu_device *vdev, struct ivpu_ipc_consumer *cons,
>  	if (ipc_buf)
>  		memcpy(ipc_buf, rx_msg->ipc_hdr, sizeof(*ipc_buf));
>  	if (rx_msg->jsm_msg) {
> -		u32 size = min_t(int, rx_msg->ipc_hdr->data_size, sizeof(*jsm_msg));
> +		u32 size = min_t(u32, rx_msg->ipc_hdr->data_size, sizeof(*jsm_msg));
>  
>  		if (rx_msg->jsm_msg->result != VPU_JSM_STATUS_SUCCESS) {
>  			ivpu_err(vdev, "IPC resp result error: %d\n", rx_msg->jsm_msg->result);