Re: [PATCH v2] serial: 8250_pci1xxxx: fix off by one in pci1xxxx_process_read_data()

[Hugo Villeneuve]

Hi,
it is not simply a matter of adding "fix" to the title.

You must explain what and why vs. how.

Please see:
  https://cbea.ms/git-commit/#why-not-how

for some guidelines on writing a good commit message.

Hugo Villeneuve


On Wed, 10 Jan 2024 22:25:21 +0300
Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:

> These > comparisons should be >= to prevent writing one element beyond
> the end of the rx_buff[] array.  The rx_buff[] buffer has RX_BUF_SIZE
> elements.  Fix the buffer overflow.
>
> Fixes: aba8290f368d ("8250: microchip: pci1xxxx: Add Burst mode reception support in uart driver for writing into FIFO")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> v2: Add "fix" to the subject.  Fix a typo in the commit message as well.
> 
>  drivers/tty/serial/8250/8250_pci1xxxx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_pci1xxxx.c b/drivers/tty/serial/8250/8250_pci1xxxx.c
> index 558c4c7f3104..cd258922bd78 100644
> --- a/drivers/tty/serial/8250/8250_pci1xxxx.c
> +++ b/drivers/tty/serial/8250/8250_pci1xxxx.c
> @@ -302,7 +302,7 @@ static void pci1xxxx_process_read_data(struct uart_port *port,
>  	 * to read, the data is received one byte at a time.
>  	 */
>  	while (valid_burst_count--) {
> -		if (*buff_index > (RX_BUF_SIZE - UART_BURST_SIZE))
> +		if (*buff_index >= (RX_BUF_SIZE - UART_BURST_SIZE))
>  			break;
>  		burst_buf = (u32 *)&rx_buff[*buff_index];
>  		*burst_buf = readl(port->membase + UART_RX_BURST_FIFO);
> @@ -311,7 +311,7 @@ static void pci1xxxx_process_read_data(struct uart_port *port,
>  	}
>  
>  	while (*valid_byte_count) {
> -		if (*buff_index > RX_BUF_SIZE)
> +		if (*buff_index >= RX_BUF_SIZE)
>  			break;
>  		rx_buff[*buff_index] = readb(port->membase +
>  					     UART_RX_BYTE_FIFO);
> -- 
> 2.43.0