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

["Padhi, Beleswar" <b-padhi@ti.com>]

On 9/30/2026 9:43 AM, Vignesh Raghavendra wrote:
>
> 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@ti.com>
> This looks like a bug fixes and needs a Fixes: tag?


All mbox clients of ti-msgmgr currently send 60/64 byte sized messages. 
So this
is not a bug today. It is only a preparatory patch for future mbox 
clients which
can send message sizes like 19 bytes etc.

Thanks,
Beleswar

>
>> ---
>>   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);
>>   	}