netdev - Re: [PATCH] net: em_cmp.c use unaligned access helpers

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Message-Id: <20080627.201649.95998057.davem@davemloft.net>
Date:	Fri, 27 Jun 2008 20:16:49 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	harvey.harrison@...il.com
Cc:	netdev@...r.kernel.org, tgraf@...g.ch
Subject: Re: [PATCH] net: em_cmp.c use unaligned access helpers

From: Harvey Harrison <harvey.harrison@...il.com>
Date: Wed, 25 Jun 2008 14:14:00 -0700

> Both locations are loading a big-endian value in cpu-endianness.  The
> be32/be16_to_cpu immediately afterwards seems suspect.
> 
> Signed-off-by: Harvey Harrison <harvey.harrison@...il.com>

Smells like a bug, Thomas can you take a close look at this?

> ---
>  net/sched/em_cmp.c |   11 +++--------
>  1 files changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/net/sched/em_cmp.c b/net/sched/em_cmp.c
> index cc49c93..56f1eae 100644
> --- a/net/sched/em_cmp.c
> +++ b/net/sched/em_cmp.c
> @@ -15,6 +15,7 @@
>  #include <linux/skbuff.h>
>  #include <linux/tc_ematch/tc_em_cmp.h>
>  #include <net/pkt_cls.h>
> +#include <asm/unaligned.h>
>  
>  static inline int cmp_needs_transformation(struct tcf_em_cmp *cmp)
>  {
> @@ -37,9 +38,7 @@ static int em_cmp_match(struct sk_buff *skb, struct tcf_ematch *em,
>  			break;
>  
>  		case TCF_EM_ALIGN_U16:
> -			val = *ptr << 8;
> -			val |= *(ptr+1);
> -
> +			val = get_unaligned_be16(ptr);
>  			if (cmp_needs_transformation(cmp))
>  				val = be16_to_cpu(val);
>  			break;
> @@ -47,11 +46,7 @@ static int em_cmp_match(struct sk_buff *skb, struct tcf_ematch *em,
>  		case TCF_EM_ALIGN_U32:
>  			/* Worth checking boundries? The branching seems
>  			 * to get worse. Visit again. */
> -			val = *ptr << 24;
> -			val |= *(ptr+1) << 16;
> -			val |= *(ptr+2) << 8;
> -			val |= *(ptr+3);
> -
> +			val = get_unaligned_be32(ptr);
>  			if (cmp_needs_transformation(cmp))
>  				val = be32_to_cpu(val);
>  			break;
> -- 
> 1.5.6.290.gc4e15
> 
> 
> 
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