linux-kernel - Re: [PATCH] applicom: Prevent unsigned wrap in ac

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Message-ID: <4A7F31F6.9000706@gmail.com>
Date:	Sun, 09 Aug 2009 22:30:46 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Roel Kluin <roel.kluin@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] applicom: Prevent unsigned wrap in ac_interrupt()

On 08/08/2009 05:13 PM, Roel Kluin wrote:
> unsigned i wraps if this occurs in the first iteration.

Could you elaborate? I don't quite understand the point.

> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
> Or do we know this can't happen?

You mean the i--? It's followed by i++ in the for loop 3rd expression. Or?

> 
> diff --git a/drivers/char/applicom.c b/drivers/char/applicom.c
> index 73a0765..0df3e12 100644
> --- a/drivers/char/applicom.c
> +++ b/drivers/char/applicom.c
> @@ -670,7 +670,7 @@ static irqreturn_t ac_interrupt(int vec, void *dev_instance)
>  			}
>  			Dummy = readb(apbs[i].RamIO + VERS);
>  
> -			if(readb(apbs[i].RamIO + RAM_IT_TO_PC)) {
> +			if(i && readb(apbs[i].RamIO + RAM_IT_TO_PC)) {
>  				/* There's another int waiting on this card */
>  				spin_unlock(&apbs[i].mutex);
>  				i--;
--
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