Re: [PATCH v2] tty: serial: fsl_lpuart.c: prevent a bad shift operation

[Greg Kroah-Hartman]

On Tue, Jul 21, 2020 at 11:12:29PM +0530, B K Karthik wrote:
> prevent a bad shift operation by verifying that
> the argument to fls is non zero.
> 
> Reported-by: "Vabhav Sharma (OSS)" <vabhav.sharma@xxxxxxxxxxx>
> Signed-off-by: B K Karthik <bkkarthik@xxxxxxxxxxxx>
> ---
> v1 -> v2:
> 	added Reported-by tag
> 
>  drivers/tty/serial/fsl_lpuart.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index 7ca642249224..0cc64279cd2d 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1168,7 +1168,8 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport)
>  	 * 10ms at any baud rate.
>  	 */
>  	sport->rx_dma_rng_buf_len = (DMA_RX_TIMEOUT * baud /  bits / 1000) * 2;
> -	sport->rx_dma_rng_buf_len = (1 << (fls(sport->rx_dma_rng_buf_len) - 1));
> +	if (sport->rx_dma_rng_buf_len != 0)

How can this variable become 0?

thanks,

greg k-h