Re: [PATCH] bus: mhi: ep: Fix off by one in mhi_ep_process_cmd_ring()

[Alex Elder <elder@linaro.org>]

On 1/26/23 3:29 AM, Dan Carpenter wrote:
> The > comparison should be changed to >= to prevent an out of bounds
> access into the mhi_cntrl->mhi_chan[] array.  The mhi_cntrl->mhi_chan[]
> array is allocated in mhi_ep_chan_init() and has mhi_cntrl->max_chan
> elements.

You're right.  I scanned through that file and there
are other spots that don't check that the channel ID
is in range, though I think this is the one where it's
reading it from an external source.  I.e., the other
places are aleady known to be correct.  (Maybe Mani
can comment.)

Reviewed-by: Alex Elder <elder@linaro.org>

> 
> Fixes: 2527ad44ddb2 ("bus: mhi: ep: Check if the channel is supported by the controller")
> Signed-off-by: Dan Carpenter <error27@gmail.com>
> ---
>   drivers/bus/mhi/ep/main.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> index bcaaba97ef63..be2d56e7f392 100644
> --- a/drivers/bus/mhi/ep/main.c
> +++ b/drivers/bus/mhi/ep/main.c
> @@ -125,7 +125,7 @@ static int mhi_ep_process_cmd_ring(struct mhi_ep_ring *ring, struct mhi_ring_ele
>   	ch_id = MHI_TRE_GET_CMD_CHID(el);
>   
>   	/* Check if the channel is supported by the controller */
> -	if ((ch_id > mhi_cntrl->max_chan) || !mhi_cntrl->mhi_chan[ch_id].name) {
> +	if ((ch_id >= mhi_cntrl->max_chan) || !mhi_cntrl->mhi_chan[ch_id].name) {
>   		dev_err(dev, "Channel (%u) not supported!\n", ch_id);
>   		return -ENODEV;
>   	}