Re: [PATCH 2/2] mailbox: ti-msgmgr: Read exact number of trailing message bytes

[Vignesh Raghavendra]

On 30/09/26 01:31, Beleswar Padhi wrote:
> ti_msgmgr_send_data() copies the message to the data registers in u32
> units. This has been harmless so far because the clients (TI-SCI)
> always passed its preallocated message buffer, which is sized to the
> maximum message size (60 or 64 bytes, a multiple of 4), so the extra
> bytes read were still within the buffer. But, with a later TI-SCI
> update, the message size can be varying now and not guaranteed to be a
> multiple of 4, which would trigger KASAN out-of-bounds reports.
> 
> Therefore, Build the trailing word by reading one byte at a time, only
> up to the message length. The value written to the register is
> unchanged.
> 
> Signed-off-by: Beleswar Padhi <b-padhi@xxxxxx>

This looks like a bug fixes and needs a Fixes: tag?

> ---
>  drivers/mailbox/ti-msgmgr.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mailbox/ti-msgmgr.c b/drivers/mailbox/ti-msgmgr.c
> index 425d5f9d9d0e3..44457a896510f 100644
> --- a/drivers/mailbox/ti-msgmgr.c
> +++ b/drivers/mailbox/ti-msgmgr.c
> @@ -425,10 +425,18 @@ static int ti_msgmgr_send_data(struct mbox_chan *chan, void *data)
>  
>  	trail_bytes = message->len % sizeof(u32);
>  	if (trail_bytes) {
> -		u32 data_trail = *word_data;
> -
> -		/* Ensure all unused data is 0 */
> -		data_trail &= 0xFFFFFFFF >> (8 * (sizeof(u32) - trail_bytes));
> +		/*
> +		 * Read the trailing bytes one at a time instead of as a full
> +		 * u32, as the message buffer may end right after them and a
> +		 * u32 read would go past the end of it. This also leaves all
> +		 * unused data as 0.
> +		 */
> +		u8 *byte_data = (u8 *)word_data;
> +		u32 data_trail = 0;
> +		int i;
> +
> +		for (i = 0; i < trail_bytes; i++)
> +			data_trail |= byte_data[i] << (8 * i);
>  		writel(data_trail, data_reg);
>  		data_reg += sizeof(u32);
>  	}

-- 
Regards
Vignesh
https://ti.com/opensource