netdev - Re: [PATCH net-next] htb: fix sign extension bug

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Message-ID: <1375450580.3927.12.camel@edumazet-glaptop>
Date:	Fri, 02 Aug 2013 06:36:20 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	David Miller <davem@...emloft.net>,
	Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] htb: fix sign extension bug

On Thu, 2013-08-01 at 22:32 -0700, Stephen Hemminger wrote:
> When userspace passes a large priority value 
> the assignment of the unsigned value hopt->prio
> to  signed int cl->prio causes cl->prio to become negative and the
> comparison is with TC_HTB_NUMPRIO is always false.
> 
> The result is that HTB crashes by referencing outside
> the array when processing packets. With this patch the large value
> wraps around like other values outside the normal range.
> 
> See: https://bugzilla.kernel.org/show_bug.cgi?id=60669
> 
> Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
> 
> --- a/net/sched/sch_htb.c	2013-06-20 09:22:46.489542435 -0700
> +++ b/net/sched/sch_htb.c	2013-08-01 22:12:43.736307055 -0700
> @@ -100,7 +100,7 @@ struct htb_class {
>  	struct psched_ratecfg	ceil;
>  	s64			buffer, cbuffer;/* token bucket depth/rate */
>  	s64			mbuffer;	/* max wait time */
> -	int			prio;		/* these two are used only by leaves... */
> +	u32			prio;		/* these two are used only by leaves... */
>  	int			quantum;	/* but stored for parent-to-leaf return */
>  
>  	struct tcf_proto	*filter_list;	/* class attached filters */
> --

Thanks Stephen.

Acked-by: Eric Dumazet <edumazet@...gle.com>

It seems appropriate for net tree (and stable)

We probably should report an error from htb_change_class() ?




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