Re: [PATCH] tty: serial: qcom-geni-serial: fix slab-out-of-bounds on RX FIFO buffer

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 21/12/2022 07:43, Jiri Slaby wrote:
> On 20. 12. 22, 17:15, Krzysztof Kozlowski wrote:
>> Driver's probe allocates memory for RX FIFO (port->rx_fifo) based on
>> default RX FIFO depth, e.g. 16.  Later during serial startup the
>> qcom_geni_serial_port_setup() updates the RX FIFO depth
>> (port->rx_fifo_depth) to match real device capabilities, e.g. to 32.
> ...
>> If the RX FIFO depth changes after probe, be sure to resize the buffer.
>>
>> Fixes: f9d690b6ece7 ("tty: serial: qcom_geni_serial: Allocate port->rx_fifo buffer in probe")
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> 
> Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
> 
> This patch LGTM, I only wonder:
> 
>> --- a/drivers/tty/serial/qcom_geni_serial.c
>> +++ b/drivers/tty/serial/qcom_geni_serial.c
>> @@ -864,9 +864,10 @@ static irqreturn_t qcom_geni_serial_isr(int isr, void *dev)
>>   	return IRQ_HANDLED;
>>   }
>>   
>> -static void get_tx_fifo_size(struct qcom_geni_serial_port *port)
>> +static int get_tx_fifo_size(struct qcom_geni_serial_port *port)
> 
> ... why is this function dubbed get_tx_fifo_size(), provided it handles 
> rx fifo too? And it does not "get" the tx fifo size. In fact, the 
> function sets that :).

I reads the FIFO sizes from the device registers, so I guess that was
behind the naming.

> 
>>   {
>>   	struct uart_port *uport;
>> +	u32 old_rx_fifo_depth = port->rx_fifo_depth;
>>   
>>   	uport = &port->uport;
>>   	port->tx_fifo_depth = geni_se_get_tx_fifo_depth(&port->se);
>> @@ -874,6 +875,16 @@ static void get_tx_fifo_size(struct qcom_geni_serial_port *port)
>>   	port->rx_fifo_depth = geni_se_get_rx_fifo_depth(&port->se);
>>   	uport->fifosize =
>>   		(port->tx_fifo_depth * port->tx_fifo_width) / BITS_PER_BYTE;
>> +
>> +	if (port->rx_fifo && (old_rx_fifo_depth != port->rx_fifo_depth) && port->rx_fifo_depth) {
>> +		port->rx_fifo = devm_krealloc(uport->dev, port->rx_fifo,
>> +					      port->rx_fifo_depth * sizeof(u32),
>> +					      GFP_KERNEL);
> 
> And now it even allocates memory.
> 
> So more appropriate name should be setup_fifos() or similar.

Sure, I'll rename it and keep your Rb tag.

> 

Best regards,
Krzysztof