Re: [PATCH] serial: core: check if uart_get_info succeeds before using

[Nick Desaulniers <ndesaulniers@google.com>]

On Sun, May 29, 2022 at 6:46 AM Tom Rix <trix@redhat.com> wrote:
>
> clang static analysis reports this representative issue
> drivers/tty/serial/serial_core.c:2818:9: warning: 3rd function call argument is an uninitialized value [core.CallAndMessage]
>         return sprintf(buf, "%d\n", tmp.iomem_reg_shift);
>                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> uart_get_info() is used the *show() functions.  When uart_get_info() fails, what is reported
> is garbage.  So check if uart_get_info() succeeded.

Hi Tom,
Thanks for the patch. What do you think about throwing __must_check on
the definition of uart_get_info with a comment that members of the
retinfo param will not be initialized if the return value is not zero?

Otherwise, patch LGTM.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

>
> Fixes: 4047b37122d1 ("serial: core: Prevent unsafe uart port access, part 1")
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>  drivers/tty/serial/serial_core.c | 52 ++++++++++++++++++++++++--------
>  1 file changed, 39 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 9a85b41caa0a..4160f6711c5d 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2690,7 +2690,9 @@ static ssize_t uartclk_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.baud_base * 16);
>  }
>
> @@ -2700,7 +2702,9 @@ static ssize_t type_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.type);
>  }
>
> @@ -2710,7 +2714,9 @@ static ssize_t line_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.line);
>  }
>
> @@ -2721,7 +2727,9 @@ static ssize_t port_show(struct device *dev,
>         struct tty_port *port = dev_get_drvdata(dev);
>         unsigned long ioaddr;
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         ioaddr = tmp.port;
>         if (HIGH_BITS_OFFSET)
>                 ioaddr |= (unsigned long)tmp.port_high << HIGH_BITS_OFFSET;
> @@ -2734,7 +2742,9 @@ static ssize_t irq_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.irq);
>  }
>
> @@ -2744,7 +2754,9 @@ static ssize_t flags_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "0x%X\n", tmp.flags);
>  }
>
> @@ -2754,7 +2766,9 @@ static ssize_t xmit_fifo_size_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.xmit_fifo_size);
>  }
>
> @@ -2764,7 +2778,9 @@ static ssize_t close_delay_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.close_delay);
>  }
>
> @@ -2774,7 +2790,9 @@ static ssize_t closing_wait_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.closing_wait);
>  }
>
> @@ -2784,7 +2802,9 @@ static ssize_t custom_divisor_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.custom_divisor);
>  }
>
> @@ -2794,7 +2814,9 @@ static ssize_t io_type_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.io_type);
>  }
>
> @@ -2804,7 +2826,9 @@ static ssize_t iomem_base_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "0x%lX\n", (unsigned long)tmp.iomem_base);
>  }
>
> @@ -2814,7 +2838,9 @@ static ssize_t iomem_reg_shift_show(struct device *dev,
>         struct serial_struct tmp;
>         struct tty_port *port = dev_get_drvdata(dev);
>
> -       uart_get_info(port, &tmp);
> +       if (uart_get_info(port, &tmp))
> +               return 0;
> +
>         return sprintf(buf, "%d\n", tmp.iomem_reg_shift);
>  }
>
> --
> 2.27.0
>


-- 
Thanks,
~Nick Desaulniers