Re: [Patch] Off by one in drivers/usb/serial/usb-serial.c

[Mikael Pettersson]

On Wed, 21 Jun 2006 23:28:17 +0200, Eric Sesterhenn wrote:
> this fixes coverity id #554. since serial table
> is defines as serial_table[SERIAL_TTY_MINORS] we
> should make sure we dont acess with an index
> of SERIAL_TTY_MINORS.
> 
> Signed-off-by: Eric Sesterhenn <snakebyte@xxxxxx>
> 
> --- linux-2.6.17-git2/drivers/usb/serial/usb-serial.c.orig	2006-06-21 23:24:07.000000000 +0200
> +++ linux-2.6.17-git2/drivers/usb/serial/usb-serial.c	2006-06-21 23:25:12.000000000 +0200
> @@ -83,7 +83,7 @@ static struct usb_serial *get_free_seria
>  
>  		good_spot = 1;
>  		for (j = 1; j <= num_ports-1; ++j)
> -			if ((i+j >= SERIAL_TTY_MINORS) || (serial_table[i+j])) {
> +			if ((i+j >= SERIAL_TTY_MINORS-1)||(serial_table[i+j])) {
>  				good_spot = 0;
>  				i += j;
>  				break;

Where is the access coverity complained about? If it's the serial_table[i+j]
quoted above, then the original code is OK since i+j < SERIAL_TTY_MINORS is
an invariant in that subexpression.

And the other accesses to serial_table[] in get_free_serial() are also only
done when the index is < SERIAL_TTY_MINORS.

/Mikael
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/