linux-kernel - Re: [PATCH] hvc_console: prevent wrapping in hvc_console

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Date:	Mon, 30 Mar 2009 13:35:31 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Roel Kluin <roel.kluin@...il.com>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: [PATCH] hvc_console: prevent wrapping in hvc_console_print()

On Tue, 17 Mar 2009 13:19:55 +0100
Roel Kluin <roel.kluin@...il.com> wrote:

> This was found by code analysis, is it needed?
> ------------------------------>8-------------8<---------------------------------
> If we subtract too much on unsigned i it wraps.
> 
> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
> diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
> index 94e7e3c..d06313c 100644
> --- a/drivers/char/hvc_console.c
> +++ b/drivers/char/hvc_console.c
> @@ -161,10 +161,10 @@ static void hvc_console_print(struct console *co, const char *b,
>  			}
>  		} else {
>  			r = cons_ops[index]->put_chars(vtermnos[index], c, i);
> -			if (r <= 0) {
> +			if (r <= 0 || r > i) {
>  				/* throw away chars on error */
>  				i = 0;
> -			} else if (r > 0) {
> +			} else {
>  				i -= r;
>  				if (i > 0)
>  					memmove(c, c+r, i);

I expect that ->put_chars() will either return a -ve errno or will
return the number of chars which were written, which will be less than
or equal to `i'.

Or maybe I miss your point.

Guys, could we have a MAINTAINERS entry for this driver please?
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