On Mon, Jun 20, 2022 at 03:20:25PM +0800, Yi Yang wrote:
> If port->mapbase = NULL in serial8250_request_std_resource() , it need
> return a error code instead of 0. If uart_set_info() fail to request new
> regions by serial8250_request_std_resource() but the return value of
> serial8250_request_std_resource() is 0, that The system will mistakenly
> considers that port resources are successfully applied for. A null
> pointer reference is triggered when the port resource is later invoked.
>
> The problem can also be triggered with the following simple program:
> ----------
> #include <stdio.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <sys/ioctl.h>
> #include <unistd.h>
> #include <errno.h>
>
> struct serial_struct {
> int type;
> int line;
> unsigned int port;
> int irq;
> int flags;
> int xmit_fifo_size;
> int custom_divisor;
> int baud_base;
> unsigned short close_delay;
> char io_type;
> char reserved_char[1];
> int hub6;
> unsigned short closing_wait; /* time to wait before closing */
> unsigned short closing_wait2; /* no longer used... */
> unsigned char *iomem_base;
> unsigned short iomem_reg_shift;
> unsigned int port_high;
> unsigned long iomap_base; /* cookie passed into ioremap */
> };
>
> struct serial_struct str;
>
> int main(void)
> {
> open("/dev/ttyS0", O_RDWR);
> ioctl(fd, TIOCGSERIAL, &str);
> str.iomem_base = 0;
> ioctl(fd, TIOCSSERIAL, str);
> return 0;
> }
> ----------
>
> Signed-off-by: Yi Yang <yiyang13@xxxxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_port.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 3e3d784aa628..e1cefa97bdeb 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -2961,8 +2961,10 @@ static int serial8250_request_std_resource(struct uart_8250_port *up)
> case UPIO_MEM32BE:
> case UPIO_MEM16:
> case UPIO_MEM:
> - if (!port->mapbase)
> + if (!port->mapbase) {
> + ret = -EFAULT;
This not a memory fault, that only gets returned for failures when
copying to/from userspace.
Please return -EINVAL or something like that.
thanks,
greg k-h
